Opening hours: Monday from 9 am to 8 pm. Tuesday, Wednesday, Thursday and Sunday from 9 to midnight. Friday from 9 am to 3 pm. Saturday from 9 am to 4 pm.
From Plaza España take bus no. 13, 23 or 150 or if you have a ticket to the Barcelona Sightseeing Bus you can use that and jump off the Bus at Montjuïc.
If you want general Travel Tips About Barcelona. What else to see in the city or where to eat then click the link