Hey thanks - there are some great freqs listed on their website!
http://www.sjifire.org/PDFs/790%20Freques.pdf
I'm amazed they put that up so publicly, in this era of public safety communications becoming more secretive. Probably not thinking about much terrorism in the San Juan Islands :)
Another San Juan Island tip - I was boating up there last summer and one thing I really wanted to do was find the whales to do some whale watching. Of course the hard thing to do is find them - they can be anywhere up there. I had heard the whale watch boats all communicated on a common frequency but this frequency is kept somewhat "secret" (probably to keep people like me from flocking to the whales all the time).
Well, I was not to be deterred, and started scanning all the VHF Marine Freqs. I finally found them on VHF Marine Channel 80 (157.025 Mhz). All the whale watch boats coordinate on that freq. We finally found the whales by listening to that freq - very cool!