Are the Borghese Gallery and the Gardens two separate tickets or are the Gardens free? Are the Gardens included in the price of the Gallery tickets. Thanks in advance!
The "gardens" are really a big park. It is not a formal flowery garden, but a big park with a couple of museums including the Galleria, a zoo, some pavilions, fountains, a lake, bikes to rent, pedal carts, etc. It's lovely for a walk if wlaking around Rome isn't enough for you. No ticket required.
Get tickets for the Galleria and enjoy a walk through the park before or after. You can walk all the way to the Spanish Steps or Piazza del Popolo if you like. Check out Villa Medici on the western edge of the park for a unique tour opportunity.
There's also a little train that runs through the park. My favorite walk is from the Galleria to the Pincio (big terrace with views of Rome), then the footpath to Piazza del Popolo, and from there down the Corso or some other street, just wandering.
The Gardens are extremely large, and of course they're even nicer when things are in bloom. Keep in mind that you need to research your destination (i.e. bus signs, cab directions, Metro stops) because the Gallery is way to one corner of a large park. The two terms are thus not synonymous. Also, in June, 2014, the closest bus stops to the Gallery were, inexplicably, out of service.
We spent the better part of 4 hrs at the park yesterday. A few were spent at the zoo. As well as the little train, you can rent segways, golf carts, bikes and kind of a bike car (seats 4 and you pedal, and I think there was a little battery powered motor to assist). We just walked, but it was lovely and cool and green in a hot city!