DH and I went to Las Vegas for his 50th birthday 5 years ago. We spent 3 nights there, and did not have a car. We flew in, took the airport shuttle to our hotel (Harrah's, on the strip) and we either walked where we wanted to go or took the transportation monorail that is behind the hotels if we wanted to go somewhere that was too far to walk.
We are not big gamblers so didn't do much of that at all, maybe about $20 worth. We did a lot of the free stuff. Many of the hotels have free things, and it's just fun to walk around and look at how they're decorated too. We enjoyed the lion exhibit at MGM, and walking around the Venetian (and took a gondola ride and our operator sang "Happy Birthday" to DH in Italian), went up to the viewing area of the Eiffel Tower, etc.,
DH wanted to have his birthday dinner at Margaritaville which was just a couple blocks from our hotel, and we had a couple meals at our hotel at Toby Keith's Bar, and ate at the hotel's buffet too. Went to a comedy show at the Tropicana.
We thought 3 nights was the perfect amount of time. We'd like to go back again, and take in some of the bigger shows next time.