Panama, Casco Viejo, Casco Antiguo
This year, St. Valentines is basically at the same time as carnivals. If you are a Panamanian, you know what this means: the city is going to be empty. Awesome.
And what a better way to celebrate an intimate weekend with your beloved one than staying in Casco. Think about it: no one will be around, you can sleep in late, walk (not take a car, ever), sunbathe at the beach or picnic there, and have a beautiful dinner at a place like Las Clementinas (228.7617 / firstname.lastname@example.org) , which has the most romantic garden in town.
A full weekend strolling hand by hand? sounds like a wonderful idea!