I was asked to do a second round of phone interview since the first one didn't go well enough to fly me onsite. I will not have more than 1 hr/day to study since I'm working 2 jobs and am behind in schoolwork. My recruiter told me I can go at whatever pace I want, but I'm worried it will be a huge red flag to ask for the interview to be scheduled for May.
I've experienced Google interviews in which I've delayed the interview process to ensure that I had a better crack at the job. It was less of a matter of worrying about my circumstances and more about communicating with their recruiter and setting their expectations in the matter.
If you're in doubt, talk to your recruiter. They are the authoritative source on the timeline that you have.
You won't miss your opportunity if you ask them for a bit of time, but you would miss it if you didn't study properly. From every Google engineer I've talked to in and outside of the interview process, taking time to study is not a bad thing.