Depends entirely on...

1. Can you get hired off-the-street as a part-timer?
2. What airframe do you get assigned? Helo's would be best, particularly the H-60 series since the CG flies a lot of those but C-130 should work too. I'm don't think the USCGR requires that you have experience in the aircraft that you want to fly, but they have a lot of applicants so it would help to have experience in H-60's, C-130's, or a Falcon Jet. They also fly the Dauphin and soon the C-144 but (with the exception of SOCOM) no other US service operates those.
3. Can you get out of your initial commitment early? Depends on manpower needs at the time.
4. Can you get hired by the USCGR? It is competitive, even amongst military-trained pilots.

If you have your heart set on the USCG, you might just have to accept an AD officer slot and take your chances on getting a flight slot after OCS. If you don't you can re-apply after a couple of years of just finish your four year (?) commitment and move on to something else in life. There are no guarantees as far as military aviation goes, your best shot is to apply for everything.

If you go that route make sure that...
1. You are medically qualified to fly.
2. Your aviation test scores are good (study before you take the tests).
3. There is a current need for USCG aviators. This one is touchy, because they may not give you a lot of options as to when you go to OCS and if the flight training pipeline happens to be backed up you might be SOL. At least verify that the flight training pipeline is flowing and that there are no USCG aviation downsizings on the near horizon. You will need to befriend a current USCG aviator to get the scoop on that when the time comes.