I have done the walk from both stations, doable in 20-30 minutes . Not much scenery , due to high walls around villas.
Bus from metro station Cornelia is very convenient to hotel . Also hotel bus is reasonably priced and runs on a set schedule .
However not good for late night return from city . Taxis are best bet late , especially if 2 or more people .
Bus takes you to Tiber river , not far from St. Peter's . email hotel and they will send schedule .
Nice property with great pool .