Look for the old Cadillacs parked out front and you're at the right place. Prague's old Havana style La Bodeguita Del Medio (named after the Havana bar, that may or may not have invented the Mojito) is two floors of live Cuban music, Mojitos, gumbo and wild salsa dancing. Awesome.
Its location means it gets a bit touristy sometimes, but if you can't beat 'em join 'em and grab one of the seats out front for an afternoon of people watching. Alternatively head to the downstairs bar after 8pm, work your way through the huge selection of rummy Caribbean drinks and hit the dance floor. If you're shy go on a Tuesday, Thursday or Friday and watch the professional Latin American dancers instead.