You can get some info at http://www.portugalvirtual.pt/_tourism/costadeprata/
I'm portuguese and I would recommend Figueira da Foz or Aveiro.
I don't know about packages but another way to get there is flying to Porto or Lisbon and then getting on a train ("Alfa Pendular", you can check the national train company site at htp://www.cp.pt)

Hello patsiej, one place you could try is Caravela tours, they go to places in portugal that the others e;g Thomson don't, we went with them last summer and are very good. They do holidays to the Algarve/Lisbon and Lisbon coast/Porto/ Madeira and the Azores, and fly from Manchester/Birmingham/Glasgow as well as Heathrow and Gatwick.
There on line site is,
http://www.caravela.co.uk
and there e mail is
enquiries@caravela.co.uk

You can order a brochure on line or give them a ring number is on line.

Dave