With only 350 hours, you'll have to do something to build time before you will be airline eligible. Joining the Guard/Reserves is a great way to build time, they pay a lot better than instructing, and you'll get top notch pilot training, for free, (heck, they PAY YOU for lessons!).

When you return from UPT, you'll be free to pursue other flying jobs to build more time, quickly, and you'll have a great fall back job if/when you get furloughed from the airlines.