Puerto Galera is nice, but if you are willing to take a short flight, you can get to many other destinations in the Philippines with better beaches. You say that you do not want to spend a large sum of money, but you can easily find promo fairs for less than $50 USD RT/person (Check Cebu Pacific, Air Phil, Philippine Airlines). Rooms can be had for less than $40 US per night depending on your destination and desire for luxury. That said, if you are set on going to Puerto, you can find rooms for about $20/night for a very standard room. Food and alcohol are both cheap and you can easily feed two of you for less than $10 (500 pesos) per meal, and that will be quite alot of food. You will be able to get a beer for less than $1.

May is not close enough to the rainy season that you need to worry about the weather, in fact it will be quite warm. Enjoy!