FWIW here's my experience: I was a banquet manager before returning to school to switch careers and a few months into school (long enough to be "sure" about switching) I thought I would tell my boss I wanted to become a software developer and had returned to school to pursue that. I assured her it wouldn't require any adjusting of my schedule (I would schedule my school around work) and that I wasn't planning on leaving the hotel until I finished my degree (i.e. years). Her response was that if I was going to leave [eventually] she'd rather it be sooner so she could hire my replacement and so I gave my two weeks notice that day.
If you think there's any chance their response would be along the lines of what I experienced I'd suggest not letting them know until you find something and then give the standard two weeks.
[Also, I don't want the above to make it sound like I left on a bad note, she was supportive and encouraging of me and she coordinated a nice going away lunch for me and we all grabbed drinks after my last shift, etc]