Excellent question - no there are no facilities available in the park

No they are not

Use the "T" Boston's subway transit system. Maps of the system are available in hotels, etc. The "T" is very user friendly.

$5 I think.

Bostonians love their pets - don't we all. Keep them on a leash and clean up - always.

Si vas con niños te aconsejo el museo de los niños, espectacular. Buen viaje

But NOT on the Gardens themselves

Yes! There are vendors within the walking paths of the park. Right across the street there are coffee shops, fast food, restaurants, pizza you can see from Boston Common. Lots of choices.

There is street parking around the perimeter of the gardens. Also, the Boston Common Garage is underground parking beneath Boston Common (right next to Boston Public Garden)

Yes. There is.