I think I'd fight, I'd hate to think I'd turn my back on my entire planet. If the aliens were like Yeerks I'd probably try to find the good ones and work with them, though not necessarily let one in my head. It depends, maybe if they ask nicely. x3
On the subject of Yeerk love, I like the idea that a Yeerk can love another Yeerk, or at least feel the love of their host for another human host ("exaggerated sympathy", rawfl). Yeerks themselves can probably feel very strong connections to other Yeerks, like friends and siblings (what about twins who work together, or that guy in #8 like morfowt mentioned). Whether it's love or not is kind of a fine line, if you grieve when a sibling dies (Aftran) or a close um, grubhood friend (Eslin in #8) is killed, or whether you abandon your own people because you love living as a human and you care enough for the other Yeerk you're with to have kids with him...I think you could call those things as much love as the love-starved Yeerks can experience. It's just new to them, that's all.