First of all, you need to realize that downtown Miami to downtown Key West is about 170 miles. So if you are planning a down and back drive, you are in for one long day. If you are overnighting somewhere in the Keys, the trip changes dramatically.
I'm going to break my answer down into several parts, starting with things to do outside of Miami, but before you get to the Keys.
There are five things I would mention between Miami and the Keys, but several of them would be a 1/2 day to full day excursion by themselves.
- Zoo Miami - located in suburban SW Miami-Dade County, is a very fine zoo with lots of interesting exhibits.
- Shark Valley, Everglades National Park -- located about 25 miles West of Miami. Walking trails with alligators every few feet in January, bicycling including bike rental along a flat 15-mile road, 2-hour naturalist-guided tour on the same road. The Shark Valley Tram Tour may be the best tourist attraction in Miami -- Google it! (And, in January, MAKE RESERVATIONS and arrive at least an hour early.)
- Big Cypress National Preserve -- the Oasis Visitor Center is 20 miles further west from Shark Valley. Beautiful cypress strands, home of the Florida Panther (which you will NOT see!), etc. If you like photography, Clyde Butcher's Everglades Gallery (awesome large format black and white photography) is 1-2 miles before Oasis VC.
- Biscayne National Park -- maybe. For now, don't bother, because there are no boat trips available. But if the park service and the boat people get their acts together by January, there may be a nice glass-bottom boat tour.
- Everglades National Park main entrance -- located SW of Florida City in SW Dade County. Very nice visitor center and a 38 mile drive with numerous stops at trails/ponds along the way. Boat tours at Flamingo at the end of the road. Keep in mind that the 38 miles is the one-way distance and it takes about an hour to drive each way without stopping.
Everglades NP currently charges a $10 entry fee, which is good for 7 days at all entrances. Big Cypress and Biscayne do not have entry fees.
Florida Keys -- There are far too many good restaurants to mention, so I'll only mention a few Keys classics. The upper keys are built-up, touristy areas with all the standard teeshirt shops and junk stores. Key West is the same, but with more character.
To understand the Florida Keys, you have to understand a few things. One, the place was founded by pirates without ships and it hasn't changed that much since. There is a real counter-culture atmosphere, especially in Key West, epitomized by The Conch Republic and Fantasy Fest. Two, the primary activities in the keys are fishing, diving, and drinking. If you don't like those things, don't go.
There are several Chambers of Commerce in the Keys and they are excellent sources of specific information about lodging and activities. All of them have websites.
Upper Keys
Two suggestions in Key Largo:
- John Pennekamp State Park, depending on the weather. January tends to be quite windy, and if the seas are too rough for a boat trip there is no sense going here. There are glass-bottomed boat tours from the park, and snorkling/dive trips into the offshore part of the park from outfitters along US 1.
- Hobo's -- great casual food.
Middle Keys
The middle keys are the pretty part. Lots of small islands with big bridges between, and beautiful water. REALLY gorgeous -- easily the prettiest place in Florida.
- I second "feed the tarpon" above.
- Sombrero Beach, Marathon -- this is one of about one good beaches in the Keys. There are two other "fair" beaches, but this is the only one I would go to. For beaches, Miami has much, much more to offer.
- Bahia Honda State Park -- this is a nice-enough beach, but most of it is on the bay side. Pretty place.
Lower Keys
- Looe Key -- a national marine preserve located (like most reef areas in the keys) about 5 miles offshore. If the weather is good, a snorkling or diving trip to Looe Key is a great experience. It's a finger reef, the top of which is about 4 feet deep at high tide. The bottom is about 40 feet, so it's perfect for either snorkling or shallow SCUBA. Amazing variety and density of marine life -- an aquatic wonderland. We have taken the boat from Looe Key Resort, and it was excellent. There are several other options.
Key West
I'll only mention a few of the things to see and do here, but there are dozens.
First of all, you mentioned beaches. On the south side of the island, Smathers Beach is a large public beach along Roosevelt Blvd. I don't like it, primarily because every time I've been there, it's been covered with seaweed. But it's the only beach in Key West.
Key West Landmarks
- Duval Street -- this is the heart of old Key West. Home of Sloppy Joe's (Hemingway's fave) and Margaritaville (and yes, Jimmy may be there), the La Concha Hotel, etc. Lots of tourist shops and bars.
- Mallory Square/Sunset Pier -- on the water at the end of Duval Street. A must do if you are overnighting is to go to Mallory Square for sunset. Lots of street performers and vendors, beautiful sunsets, big fun.
- Hog's Breath Saloon -- to buy the obligatory "Hog's Breath Is Better Than No Breath At All" teeshirt. This is the must-have Key West souvenir.
- Southernmost Point in the US - for a picture with the bouy.
- Ernest Hemingway's House -- historic tour.
Key West Restaurants
Many, many good restaurants in Key West -- far too many to list. Our two favorites are:
- Half Shell Raw Bar -- Great casual food, good service, super low-rent atmosphere which is classic Keys. If you wear an old pair of shorts, no shirt, and flip flops, you will fit in perfectly. Some of the best seafood in the Keys, and reasonable prices. This is the one place we ALWAYS eat in Key West.
- Louis' Backyard - fine dining, most of which is outside, which should be beautiful in January. A Key West tradition.