I never went to community college and can’t speak from experience there. But really, it’s not hard to maintain at least a 3.2 if you’re scheduling smartly and staying on top of things. When I say scheduling smartly, I mean not piling on a bunch of classes that you know will be very difficult. I know for me personally, the only quarters where I’ve gotten below a 3.3 average were ones where I ended up with 3-4 very hard classes. Even then, I didn’t end up that far below and my overall GPA didn’t dip lower than 3.2.
This is for a computer science/linguistics double major. And for what it’s worth, it was a lot easier to get high grades in my linguistics classes than my CS classes. Keeping at least a 3.2 still isn’t overly difficult though, especially because I got good at balancing my schedules junior and senior year.
EDIT: With regards to Ohlone vs De Anza, both are good schools and you can’t go wrong with either. But De Anza is on quarters while Ohlone is on semesters, and being on quarters to begin with would help you with your transition to UCD (or any other UC on quarters).