We love South Beach in Miami. We live in the Dallas area.
I love our weather but TX can get chilly sometimes!
No need for a car, it's a quick trip from Miami airport ( about $40) or Fort Lauderdale airport (about $100) cab ride.
No need for a car while you're there. Our favorite spot is the Loews on Collins. Wonderful beautiful hotel!! Walking distance to Lincoln Road shopping/dining and on the beach.
The Hilton Cabana is a little further north on the beach and beautiful place but not too many good things in walking distance. We ended up using a cab more from this place but loved the hotel.
Depending on the age of your daughter.... SB is very open minded and a lot of things going on you might not want her to see. The beach is topless, optional. We prefer the section furtherest north which is nicer. The furtherest southern portion can have a lot of adult activity.
We did stay at the Hilton Bently which is s nice place but it was too far south for us because we prefer to do a lot of walking. The Beacon is a classic and in the middle of everything. Clevelander is adult, no guest under 21.
Fort Lauderdale is nice too. The Marriott has a nice resort on the beach.
Marco Island is very nice and both Hilton and Marriott have great resorts there.
Miami or South Florida would probably be the warmest spot.
ETA: I have done Miami by myself and with my daughter several times with no car and had no trouble at all. I've heard wonderful things about cruises but we are just not interested in cruising.
Have fun!