Plovdiv's museums are generally fairly compact, meaning you can get around them in anything between 10-30 minutes and have good explanations in English, though they are somewhat pricey unless you take advantage of the multi-site tickets that are on offer.
 'Old Plovdiv' sites (Balabanov, Hindliyan and Nedkovich Houses, Museum of Pharmacy,Zlatyu Boyadzhiev Gallery, Dimitar Kirov Exhibition, Ancient Roman Theatre, Roman Stadium, Small Basilica) have the same price:
Adults 5 leva,  children and students 2 leva, family ticket 10 leva. Multi ticket for 5 sites 15 leva, Multi site family ticket 30 leva  More information  www.oldplovdiv.com  Tickets can be bought at the Tourist Information Offices as well as at the individual sites.

The City Art Gallery also does an all-in-one ticket price for its sites: the permanent exposition on ul. Saborna, the Icon "Gallery, the Tsanko Lavrenov and Encho Pironkov exhibitions and the temporary exhibition on the main shopping street: Adults 5 leva, children and students 3 leva.

Many of the museums  have slightly shorter opening hours during the winter months (November - April)