FOOD: No problem. I ate at the street venders many nights and had no problems.
I did get my hepatitis vaccine (highly recommended for any traveler, see your doctor and to be effective I believe immunization of some strains need 60 days). Ambergris is several notches above Mexico but there is still a lack of soap in bathrooms in restaurants. I also take 1/2 Imodium each morning..mostly to offset the change in food and beer consumption.
Almost all of the local reef diving is beginner level. The dive houses can start you off on the easiest. A good thing to do is to stay by the dive master and mimic him/her. While they stay above the group so the view is not a nice it's a great way to learn good technique. I do not recommend a night dive for a beginner as the current (tide) can be incredible.
I’d start with the Amigos Wreck (but I’ve not been to them all): 45 feet depth, moray eel should be there, great flats to hover over with many huge lobster, pillar coral. Abundant small fish, saw a turtle there.
Pillar Coral: 35’ - 80’ – 35’.
Tackle Box: 45’ – 80’ – 45’.
If she does well, love tunnel is a fun beginner dive with maybe a 50 foot tunnel (95 feet At the bottom?). Nothing down there after the tunnel. Great swim back up though the “ravines” and as usual, at about 40’. Very nice flats again.
The upper walls and tops of the channels are beautiful.
In the channels, which most dives will have, a current can surprise you around a bend and push you into the coral. It’s not strong but enough to catch you off guard if you’re going in for a look and suddenly realize there’s pressure behind you and can’t stop.
Hol Chan is one of the best shallow dives. However, there is a current so don’t get too close to the coral with an inexperienced diver.
Keep those fins up! Have a great time.