T-Mobile / Mint coverage?

I'm looking at switching my family from Verizon to Mint. I know Mint uses T-Mobile's network (but is a secondary carrier and can be de-prioritized during high-traffic times). I live in Bellingham and spend a fair bit of time out on Mt. Baker Highway area, near Deming and up at the Ski Area. I would guess with T-Mobile being an important corporate citizen here in Bellingham, that the coverage would be pretty good, but I'd like to get input from actual users of T-Mobile and/or Mint Mobile.

Thanks in advance!