Spring Training games begin tomorrow at 12:05pm Pacific and some of them (including tomorrow's) are covered on TV and/or radio. Check the link for which ones. Furthermore, it also contains all the information on Regular Season as well (99.5% just FSN and ESPN 710).
For all of those outside Seattle proper, but still within the Mariners regional area, here is a list of radio affiliates covering the games. Might be worth bookmarking.