It would be surprising if the resort you are to stay at would not print out the boarding pass for you if you give them the booking details - different if you are staying in private accommodation. If you are to be going outside Carvoeiro then stop by a library or local youth centre, both of which have public use computers and printing facilities, open weekdays only. Lagoa may have one but Portimao certainly does, in any case ask at the nearest Algarve Tourist Information office. If you have the chance of going up to Monchique then while visiting a nice local town you can get printing for free at Espace Internet (afternoons and into evening), very cheap at the library (mornings and afternoons).