If you would prefer Mediterrenan, shores of Turkey would be good these times. There will many alternatives for you like Çeşme, Bodrum, Datça, Marmaris, Kaş, Kalkan, Alanya, Kemer, Side, Demre...etc and you will be able to visit different places including archeological sites like Ephesus and Pamukkale, small lovely villages like Şirince, you would also be able to spend your nights outside and you will be enjoying sea, sand and sun.

Actually, that really depends on how far you would travel. There are quite a number of countries which are warm in May. Places like Turkey, Greece, France, Spain, any African countries, California, Hawaii, Florida, Texas, Mexico and Philippines. If you have decided which country you'd visit, then you could search for tourist spots or beach resorts that make your vacation a blast.

I definitely want to go somewhere outside US. I love the idea of turkey or greece but I just looked for example at weather in may in cesme turkey and it shows a high of 79. That won't be warm enough for me to enjoy beach/water. I'm assuming greece will have similar temperatures as well?

I'm assuming greece will have similar temperatures as well?

Correct. There is nowhere in Europe that will have near-guaranteed beach weather in May. You could get lucky, but it is not the place to go for beach weather at that time of year.

I would consider Egypt, Mexico, and Vietnam.

Çeşme is in a norther location so it's normal. Warmest place would be Antalya (Kemer, Side, Kaş, Kalkan, Demre). Marmarias and Datça would be warm too. But I recommend you to check Kuşadası'S forecast highs. (But I don't think that would be much more different)Because if you like sightseeing, Kuşadası would be very good. You can visit Ephesus and Pamukkale and also Şirince(it's a small lovely village in Selçuk and it's famous with its fruit wines.)But of course there are many sites to see also in Antalya and you can go on a boat tour and visit small islands with ancient ruins. Greece would be the same. You can also visit Northern Cyprus. It's warm even in March there.

And I also liked the idea of Egypt. You should go to Sharm el Sheikh. Swimming in Red Sea would be a great experience for you if you haven't tried it. Red Sea is very beautiful with colorful rare fish and beautiful corals. You can go on a glass-boat tour.(the ground is glass so you're able to see underwater life) You will also be able to make safari in Sinai Desert(I didn't try it) and of course to dive in Red Sea. You can visit Cairo for one day. It takes about 8-10 hours (i'm not sure because it was night when we took the road)

Mexico

Also I was thinking belize and el salvador.

cartagenainfo.net for me
casaviena.com
spirit.comcheap flights down
a couple of hours south of MIA
exotic historic close cheap great beaches.

For more adventure warm then nexussurf.com 42 perfect beaches.

Flight costs are a real budget buster to Europe
spirit.com cheap flights down to Cancun also
yucatantoday.com lots of cheeap little places and historic
ruins around ecotulum.com Cabinas Zazilkin primitive but beautifu; under $10/day