Never rented a bike there , but worked in Lisbon and Cascais in the late 90's , and have been on holiday there since then . My favourite City and the MotoGP racetrack at Estoril is next to Cascais .
Great nightlife , great food , and very friendly people , plenty of history ,lots of shops, underground is easy to use . and as a previous poster has said Sintra is worth checking out and not too far from Lisbon .