I have often hired people and they tell me upon hiring that they have a planned trip from X-X date and would it be okay to take that as unpaid leave. I always say "yes." I don't expect people to not plan their lives just because they are unemployed. I think a lot of employers are okay with this. I would plan your trip, and if you get a new job, just tell them that you need some unpaid leave for the time of your trip. I have seen this happen at almost every place I've worked. It's typically not a big deal.