If getting the train I too would advise getting the train to Aston, Witton is most definitely a quicker journey door-to-door but if you get off at Aston the first thing you'll see of Villa Park is the Holte Pub/ Holte End (magnificent) whereas Witton it would be the North Stand (underwhelming). You will also pass Aston hall this way, although it will be likely shut/dark.
Also, if having a drink or two, getting off at Aston would mean passing by the Aston Tavern en-route to the stadium, arguably the busiest/closest pub to the Holte.
Otherwise it's a taxi and with that Birmingham is your oyster, I see from previous posts you like the look of the Barton Arms, after that it would be a 20min walk or a taxi as close to the ground as possible (traffic will get heavy close to kick off so don't cut it too fine).