By far the most flexible way to get around is to hire a car at the airport (you get a slightly better price hiring through the Ryanair web site before you fly, and they do actually sell out sometimes at the busiest times of the year).
The drive to Penne is a bit under an hour without rushing. The route described here is not the only one, or the shortest, but it is the simplest: you just take two 'A' roads: the SS5, followed by the SS81.
Coming out of the airport, turn right onto the SS5 'Tiburtina' inland towards Chieti and the mountains and away from Pescara. Don't follow signs to Chieti - they lead to the motorway, which you don't want - your road is signposted 'Sambuceto'. If you arrived in the evening and want to stock up on food before setting off to Penne there is a large supermarket called Auchan immediately after the airport on the right.
Stay on the SS5 for around 5 kilometres, until you reach the first roundabout. This is a miniroundabout under the SS81 flyover and has a (hard to spot) signpost to Penne. You need to get up onto the flyover. Turn left at the roundabout, and bear left over the second mini roundabout immediately afterwards to get onto the access ramp. You should now be heading north on the flyover, and soon cross a long bridge over the river Pescara.
The SS81 is a busy road which goes all the way to Penne. Penne is well signposted. The only real chance of a mistake is at the entrance to Cepagatti, where what is signposted as a right bend is actually an abrupt right turn half-hidden behind a church.
From Cepagatti the traffic thins out. Just keep on the SS81 following the signs to Penne and heading through the hills towards the Gran Sasso: the mountain which dominates Penne, and one of the few to keep some snow cover throughout most of the year.
The SS81 into Penne climbs a very long hill past modern housing, sports centre, and supermarkets. At the very top you come to the municipal gardens and the spectacular main gate. Keep following round the walls past this. You have a choice of two entrances to the town: one which passes the house, and one which allows you to park nearby. On first arrival you may prefer to park outside the walls and walk in: the nearest carpark is free (but it is a steep walk in). You can zoom in on the map of Penne to see the exact location of the house.
Drive round the outside of the town to the third entrance. This is a very sharp right, which will take you two attempts. Drive in through the entrance and follow the narrow road to a small square; turn right by the church here into Via San Panfilo.
At the end of the road is a church yard which you can park in; alternatively, drive up the slope at the side of the churchyard and you may be able to park at the top. If you want to drive past the house itself to drop bags off (you won't be able to park there),
then turn sharp left here along Strada Santo Agostino - which is just wide enough for most cars - and keep going till a single-story house with a metal fence round a roof patio; number 58 is just in front of this, on the right.
Follow the road round the town till the petrol station. The road into the town is an extremely sharp right immediately after the petrol station; this will take you two attempts. Drive through the small gate, check the road is clear in the street mirror, and turn sharp left up the steep hill.
Carry on past the fountain and park wherever you can - there are often empty spaces in front of the big palazzi on Via Muzio Pansa. You are now slightly above the house, which you can reach either
from the alley which runs down from the yellow house or by walking back to the fountain and turning left into Strada St. Agostino.
The house does not have its own parking. You can park close by, either in front of the big palazzi along the road above the house (Via Muzio Pansa), or by the church at the end of Via St. Agostino. However, all driving in the town is banned on the numerous feast days etc (well signposted in advance).
Alternatively, there is municipal parking all round the town just outside the walls. The multi-storey carpark by the petrol station is free; some others charge (they have ticket machines - the rates are minimal).