Visitors will enjoy the best weather during the dry season from December through May (though occasionally winter storms called "northers" will hit the coast between December and February). The rainy season, which also corresponds with hurricane season, runs from June through November. If you're willing to chance a few showers, you can often get cheaper lodging rates during the rainy season; you'll also find smaller crowds on the beaches and at the most popular Mayan ruins. Temperatures are balmy year-round, but warmest during the spring and summer.
Although the cost of living is higher here than in other Central American countries, Belize is still an extremely affordable destination for visitors. The Belize dollar is pegged to the U.S. dollar at a ratio of 2:1, so it's easy for Americans to monitor their spending (and U.S. dollars are an acceptable or even preferred payment in many places). Hostels, small independent inns and even the occasional campsite will suit travelers looking for budget lodging. There's always at least one cheap option on every menu: the ubiquitous (and delicious!) Belizean beans and rice.