These are the things I tend to keep on hand all the time:
Frozen vegetables
bagged salad mixes
eggs
aluminum cup cake holders-to make the vegetable quiche cup thingys. These are great, make a couple batches with different vegetables so you don't get too bored, freeze them and you can have breakfast for the whole week.
canned tuna and salmon
several cans of beans, black and chickpeas are my favorites.
low fat/part skim milk cheeses-the fat free takes a little getting used to, also some brands of fat free cheeses are better then others.
Get the smallest riccotta cheese you can to see if you like the brand, some brands are grainier then others and it would be sad to get the big 2 pounder just to find out you hate that brand.
One of the things I had problems with when I first started was buying too many vegetables at a time. You can always go back to the store if you run out.
I would buy so much that some would actually go bad before I got around to eating them. Or I found I had about 2 weeks worth shoved into my fridge. I also would buy several new vegetables a week and too much of it and found that many of them I didn't like. I live near an asian market and would pick up some strange things. Now, I limit myself to 1 strange thing and only a handful and if I like it I'll get more next week.
I tend to stock up on chicken breast and other lean meats when they go on sale. I keep a couple pounds of cooked chicken breast in the freezer, I can take some out and throw on a salad or what ever.
Low fat and fat free deli meats- handy for snacks and meals too I guess- roll up with some vegetables and a sliver of cheese, yum, yum.
Salad dressings with 3 grams of sugar or less per serving
some sort of Mayonaise-
Good luck on the Beach. It's a great way of eating.