Marc Anthony -- Partying Like a Single Guy

Marc Anthony doesn't need J.Lo to have a good time ... 'cause dude seemed to be having a blast in Costa Rica this week while some chick planted a big, fat kiss on his cheek.

Anthony -- who separated from his baby mama back in July -- threw a HUGE party a few days ago to launch his new TV show ... a Latin singing competition called "¡Q’Viva! The Chosen," which is set to debut in early 2012.

We're told Marc got behind the DJ booth for a while a spun a couple of records -- and later took a couple of cozy pictures with a woman named Dianna Perez, who's part of the crew.