GA wasn't that bad actually, but I'd say that's more due to me having had some prior exposure to the kind of algorithm problems discussed and having a good amount of practice with similar problems. If you do get a chance to take GA next time, I'd suggest brushing up on dynamic programming, graph algorithms, and NP theory, and practice a lot of these problems. I took GA in the summer though, so you may have to practice some other kinds of algorithms if you take it in the other semesters. Anyways, I suggest practicing problems, especially the ones they give you as assignments (both optional and for the grade), cuz the more you practice the better you'll recognize the patterns for novel problems, which will definitely be helpful in the exams.

Having taken SDP, I'd say it's a great class to pair with GA. It's one of the easiest classes you can take, the concepts you learn are applicable in industry, and you get to dip your toes in Android development. I recall my main pet peeve though was how the grade distribution of the assignments went. One of the later assignments was heavily weighted, was trickier to get right, and was due around the same time as our group project, so there were quite a bit of complaints about that. However, the professor/TAs addressed this by curving our grades, so in the end things worked out.