Before planning your trip, it's a really good idea to research events, especially holidays, for the country you want to visit.

Some places, like Costa Rica, are deserted around Easter and Xmas, so you want to avoid travel to those countries during that time if you are seeking out girls.

I went to Thailand during Songkran, an annual holiday/water-festival event they hold each year. (sorry, I forget exactly what it is) Anyways, most guys seem to think it's a blast with people shooting you with water guns and drenching you buckets. They also run around trying to get flour on your face. For me personally it was a pain in the ass. I hate walking around in wet clothes, more so when walking into air conditioned bars. And when you're kissing several girls a day on top of that, it's not the best combination for staying healthy.

Anyways, I found this link which many of you should find useful. One of the options allows for you to search for holidays for each country, and it will generate the specific date for the year you select.

http://www.earthcalendar.net/index.php

I second that emotion: the last thing you want is arrive in a city where absolutely nothing is happening because (a) the locals are all away on vacation, or (b) the girls have gone home to visit their families.

Look out for religious holidays, especially in Catholic countries, and skip France and Italy in August.