Normally, if going abroad for a reasonable period, I get a local pre-pay SIM
as it normally works out a lot cheaper, mainly because of no charge for
incoming. (Eg Ireland, Australia New Zealand) or use a United Telecom SIM.

I'm going to Canada (Alberta/BC) and Washington State soon, but it seems
like it's not so straightforward in N. America.
Is it viable to buy a local SIM in Canada or US to reduce costs? United
Telecom charges are particularly steep for N. America so I'd like to know if
an alternative is available.

(And before anyone asks, I have an unlocked tri-band phone)

Thanks
Bob Coates