You can arrive on Friday and get married on Monday. My daughter did that last September. As NY Gal says, there are a lot of other condiderations too. We used Iraida at belizeweddings.com to help us. She did all the paperwork, arranged the minister, flowers and a photographer. She also helped us to decide where to stay and to have the wedding. We stayed at Carribbean Villas and had the wedding on their beach. Great place and a very pretty beach. My daughter wanted to get married at dawn on the beach since San Pedro is on the East side of AC, but it seems most mornings are cloudy and you really take a chance that you will have a pretty sunrise. She switched to a sunset wedding and it was beautiful (plus, we didn't have to get up at 4:00 or 5:00 in the morning)
It rained earlier in the day, but by sunset all rain was gone which, from reading this board, seems the way most rainy days are. Congratulations on your wedding. I'm sure you will have a great time on AC.