An interesting fact. Spanish isn’t spoken very often in Belize. You’re more likely to hear English…. the official language of Belize, or Creole, Garifuna, and Mayan. You can find Spanish speakers, but I didn’t hear it alot till I got to Guatemala.
That said, I loved Belize. It sounds like you might be a good match for Placencia. We stayed at the Maya Beach Hotel, which warns on its website that they are not a luxury spot, but read my entry, and you will see why it is a fantastic place. Also the monkey river is there for birdwatching and kayaking. And the caribbean sea. There was even a boat trip (we went scuba diving), where you have lunch on a island that is also a bird reserve. Check out this link as well.
Good luck in planning your trip. I know Costa Rica is wonderful, but Belize will always be special to me. One of my favorite trips. Avoid Belize City altogether, and if you have any questions let me know. I stayed on Ambergris Caye, in Placencia, and San Ignacio. I also went to Jaguar Paw, and many places in between. We used a car to get around as well. I took the picture while in a boat on the monkey river.
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I second the advice about avoiding Belize city. I stayed in Placencia, it was a delightful trip. I stayed at “Singing Sands”.
I also went to Costa Rica, from San Jose we went directly to Quepos, Damas, and Manuel Antonio.
If I had to choose a place to go back, I’d go back to Costa Rica, despite my not having spanish.