Family from out of state rents a cottage there every summer for 2 weeks. I work a job that has rotational on-call work where I either need Wi-Fi or somewhat decent cell signal..

I have been using Mint Mobile for ~2 years myself. The service uses T-Mobile and Sprint towers and has great coverage in the Greater Portland area, the only issue area I have run into so far is Higgins Beach in Scarborough, but that has been an issue with every provider I have tried in the past as well.