If you choose not to tell them up front that you're gone after two months, then that most likely means that you're also choosing not to use them as a future reference.

Nevertheless, it's not impossible to get a busy time off shortly after starting a new job, though my circumstances may have been more valid than yours. I'm going to school in a different city from home, and I live in my school's residence. They kick us out of residence during winter break, so I had to fly home for the break. I started a job (fashion retail) at the beginning of November, and at the interview I told them that I wouldn't be here for the holidays, and they hired me anyway.