In terms of TS locations, inside
Disneyland, the Blue Bayou is the most iconic restaurant. It gets mixed reviews on the food, but I've always enjoyed my meals. I would aim for the first seating of the day (11:30 am) and request a waterside table. For a similar style of cuisine, Cafe Orleans is a good choice. I also like Big Thunder BBQ (all-you-care-to-eat/family-style) and Carnations Cafe (fried pickles!).
In DCA, my favorite TS location is Carthay Circle. It also gets mixed reviews, but I've enjoyed my meals. It's a very pretty looking restaurant. If you have the chance to take the free tour in the morning, I would recommend it. It'll give you a little history of the building it's based on and it's significance in Disney history. Carthay also has a WoC dining package...and it has all indoor seating.
In terms of the CS locations, there is quite a variety of places and styles (think kind of like Epcot). In DL, I really like the Plaza Inn (Fried Chicken), Redd Rockett's (salads), and my favorite is French Market (everything!). I highly recommend the French Market because it has amazing food and is a great spot to do some people watching. The Mint Julep window sells Mickey beignets and DL's version of a non-alcoholic mint julep (it doesn't taste much like a real mint julep, but I like this one better!).
Over in DCA, I like Boardwalk Pizza and Pasta, which is also next to Paradise Grill. The Boardwalk has good salads and flatbreads. Flo's (in Carsland) has a good selection of "comfort foods" and you can watch Carsland and/or RSR as you dine. There are also lots of CS dining options over by the Wharf area, but I've had mixed results there.
In general, it isn't as hard to get dining reservation or even find walk-ups at DLR as it is at WDW. That being said, if you know you want to eat somewhere at a specific time, I would make an ADR. ADRs open up 60-days in advance, so you have a few more days to go before you can make an ADR.