I want to take my daughter age 26 on a short "sun" vacation the first week of March. Miami Beach is on my short list but I want to make sure it won't be over crowded with spring break teens. Also, any advice on hotels on the beach that under $200/night?

Easter is the first week of April this year. The first week of March will be before most spring breaks. You'll still have snow birds and early breakers, but not a bad time.

Both the South Beach and Miami Beach Marriott Courtyards are at $199 first week of March. I prefer the South Beach location.

You can walk to South Beach restaurants, shops and clubs from this location. I might not walk back late at night, but it's a short cab ride.

Thanks for your help. Would a day trip to the Keys be feasible?

It depends on which Key -
Key West is not a day trip, however, Key Largo is possible.

The Courtyard on South Beach is not on the actual beach it is on Washington Ave. which is a few blocks from the water- not sure if that matters to you. The Miami Beach Courtyard is just across the street from the ocean, but not on South Beach - its further north.

The Courtyard I am recommending is Miami Beach Oceanfront, not the one on Washington. I've stayed at the one on Washington. It's okay, but not near the ocean.