My quick Belize recommendations

we were in Belize for 15 days spit between San Ignacio, Placencia and Ambergis Caye. Depending on how much money you want to spend and what you want to do depends on what i would recommend. I would recommend renting a car if you are not going to stay on islands.
We rented a car from Belize airport and drove to San Ignacio, then to Placencia.

 In San Ignacio we did Crystal caves - very cool and mostly untouched caves, not sure how much longer they'll let people down there. Not sure what this tubing thing is mentioned on trip advisor, maybe you can tube when waters are lower? we just scaled down a cave for a few hours and its a tough climb out from the bottom. comfortable with heights is a good thing, but it's not too bad. http://www.tripadvisor.ca/Attraction_Review-g291970-d1137844-Reviews-Crystal_Cave-Belmopan_Cayo.html. "Diego" was our guide, he was kind of nuts but awesome and serious when need be since there are a couple somewhat sketchy places you need to go.

We also did a tour to Tour from san ignacio to tikal, guatemala. it was worth going to see. Elias was our guide: http://www.belizeculturetours.com/

my parents friends, (canadian)friends, own https://www.flipkey.com/san-ignacio-villa-rentals/p661245/ and rent it out. it is out of the town of San Ignacio a bit, but kind of nice to cook our  own stuff and drink a bunch of Rum there

Placencia was mostly about scuba diving. we tried snorkeling for a bit off out of our cabana at Trade Winds but not much was to be seen. All the restaurants and a bunch of hotels/pubs are mostly owned by Canadians here. there are a couple places to watch sports and get some good adult beverages, but also very relaxing to stay on your patio at the cabana and watch the fishing boats come and go.

the last part of our adventure was to ambergris caye. i don't have much positive to say about it, other than the scuba diving was cheap and only took a couple hours instead of a full day (like in Placencia). there are more restaurants/pubs and whatnot, but it was more touristy and expensive. by the time we made it here we were starting to want to watch our money a bit. Ambergris is the most well known tourist destination of belize, lots of americans/europeans alike. only good thing is like i said, the scuba was close and snorkeling and the "blue hole" is closest to here.