manderin if your gonna bother. first its closer to how you write in chinese, cantonese is not so close.. a bother to learn 2nd the usefulness of cantonese is limited since the vast majority of chinese use manderin, and even cantonese know manderin. 3rd.. well i think manderin sounds better, my parents agree. i just find some languages more elegant, other ones just have icky noises i'm cantonese i think you can judge languages by how they sound sorta bad example, but klingon sounds pretty bad eh? hehe gutteral i guess. anyways, hong kong movies are in both cantonese and manderin. i'm not sure if i'd suggest learning from them since about 90% of hong kong movies are garbage
oh yes, call your g/f a "bahk poh", she'll love it
also chinese isn't just something you should do to impress your g/f, it looks good on your resume heh