Trying to come up with a love song in Spanish? All you need is one semester of Spanish, and you're golden. Google translator helps, and so does Spanishdict.com.
But you might also want to bring an authentic, Latin-inspired meal that you can pick up from any hole-in-the-wall Latin food place. This will help your loved one forget how sh*tty your Spanish is, and how your accent is subpar.
But, just remember that you tried. And that's very important. :)