Where can gay guys go on vacation?

Fire Island. (Sorry, that might be a bit out of date!)

Seriously, you can go anywhere. But there are also travel agencies that cater for gay tourists and will point you towards particularly gay beaches and resorts.

Key West, Miami, Atlanta, San Francisco. , New York, INC... Gay's people can go to the same vacation spots as straight people.

You should be aware that some countries still have anti-homosexuality laws that forbid homosexual acts. It is always good to research before you travel.