Best way to handle? Job Question

I have one job offer that I'm unsure about. I have had two interviews with a different company, and honestly feel good about it - but I am suppose to get back to job #1 as soon as possible about accepting the job - and I haven't heard from job #2 yet. The lady just got back from vacation so I hoped to hear either yestersay or today. I just wasn't sure if I should send an email being honest that I have another offer but they are my first choice? Or wait it out? I just would hate to turn down #1 if I don't even get #2. What's the best way to handle?