My time in this country was amazing! If you need evidence, just read a couple of posts about my days there. Of course every country has awesome experiences to offer, so why Belize!? Here's the quick rundown.

Reasons to Choose Belize

Central American hospitality at it's finest with a pace of life that is relaxing and peaceful
The national language is English, so there is minimal language barrier
Cheap to fly there and cheap once you're inside the country (1 usd= 2 Belize dollars) Usd is accepted as legal tender everywhere. No need to exchange. Biggest expense is taxis
Small country so it is easy to get around.
Beautiful beaches and dense jungle.
Not overcrowded with tourists and traditional western resorts. Easy to get a taste of the culture.

San Pedro

Must See's in Belize

Actun Tunichil Muknal: Mayan Cave ruins in San Ignacio. If you visit Belize and forgo this venture, no matter how out of the way it might be, you are missing out on one of the coolest experiences you may ever have
San Pedro or Caye Caulker: San Pedro is the more populous and popular of the two islands in which you must take a water taxi from Belize City to get too. If you're looking a quieter place, choose Caye Caulker, although San Pedro is my recommendation. Lots to do there.
Secret Beach in San Pedro: Will have to rent a golf cart and ask for directions. Also a 45 minute drive, but worth every minute. Windless, clear, and quiet; if you can't relax here, then you can't relax anywhere.
Also recommend traveling during the winter (December-February). Weather is perfect. You will avoid rainy season and the sweltering humid summer.

What to Skip

Don't bring too much luggage. It is a hassle. This is just really a travel tip in general
Belize City: I didn't really spend much time here, but I think time is spent better elsewhere.
Snorkling or Snuba: Unless you are new too either I would skip. Snuba was great, but I am ready to do some real diving. If that is you're calling, Belize has the famous blue hole and many other amazing dives.

Now I give these recommendations, but there is so much more to do in the country and so much I missed, so don't just take my word for it. Research yourself and make your own journey into the country, because it's a amazing place with amazing people who are ready to share their culture and national treasures.