Best Romanian Coursebook?

Hi,

which coursebook can you recommend for learning Romanian? I am German and already speak English and Portuguese. I've been to Romania several times and have some basic practice and knowledge about the Romanian language. Now, I'd like to study intensely so I'll be able to do some conversation when visiting Romania in July/August 2013.

Does anybody have some advice for me? Later on, a tandem partner would be nice, too. =)

Kind regards,

johas