I think a lot of Florida would suit you as much of Florida is suburban in nature.
Most of the major Florida cities are gay-friendly, but some have more significant gay communities. I'm in Jax, and though the city is fairly gay-friendly, the gay and lesbian communities here are small.
I'd look closely into your brother's needs. Social Services seem to be lacking all over Florida and you may not find the support he needs everywhere here - it is not like NY. If he needs particular types of doctors/support groups/etc., I'd be certain those were in place before making any moves.
Orlando is okay, it wouldn't be my choice (no Ocean, too much Disney, too hot in the middle of the state, etc.), but there is nightlife and plenty of people (maybe TOO MANY people based on what you're looking for

).
If you're willing to live in the middle of the state, have you thought about Gainesville? If you're coming from the Catskill Mountain area, Gainesville might be your speed (might find good care for your brother there too).