There'll be parking in Perry Hall Park, close to Perry Park. You can't buy parking in advance but it will be for sale on the day for £15 - they don't expect to sell out. You can't buy three-day tickets or leave cars overnight.
Birmingham has three train stations in the city centre; New Street, Snow Hill and Moor Street.
These are the buses going directly to Perry Park:
Walsall Road; 51 (up to every 8 minutes), X51 (up to every 15 minutes), 952 (up to every 15 minutes).
Aldridge Road; 33 (up to every 8 minutes), 907 (up to every 15 minutes), 934/935/936 (up to every 10 minutes), 997 (up to every 10 minutes).
These buses will all stop on Moor Street Queensway, Lower Bull Street and Corporation Street in Birmingham city centre and will run until around 23:30.
There are other services passing close by.