I heard the weather in March is better as well. Isn't August during the hurricane season? It really depends on your job change situation. If you ask me, I say March! Who wants to wait a year to get married in paradise?
We were sort of in the same position. My fiancee and I were considering waiting until December of 2010 instead of this December for financial reasons. I didnt think I could wait that long though and figured we were saving so much already by not having the big huge wedding. He is in the middle of a big job change as well so we are tight on the money end but we decided that this December is right for us.
Only you can decide how long you want to wait for. But, I would be nervous about hurricanes affecting your wedding plans in August.
We just married in late August. We had a quick hurricane scare with Bill but thankfully, all worked out fine. (Always purchase trip insurance, anyway) If you prefer March though, go for it! I couldn't wait that long either, which is why we chanced it with August. We didn't want to wait until the following Spring! You can save that money after you get back and pay off what's needed!! Good luck.