There used to be a really nice tropical island sim called Adele, up until a few weeks ago. Hardly anyone ever visited, so it was quite tranquil. I tried to visit yesterday, however, and found out that it had been bought out and turned into someone's private home, which was sad.
Miami is always crowded, but it has never been very friendly. It might be worth checking out. New Brighton has several beaches, but hardly anyone goes there.
My top recommendation would be the Da Vinci Gardens, which has a tropical island area and a reasonable visitor count. I think that it's rated Moderate, but might even be General. Well worth a visit. On arrival, there's a screen up somewhere with TP links to the different areas.