San Francisco is filled with some of the most pet-friendly people you'll ever meet. If you're planning to bring a pet with you to San Francisco, it's important to look for a neighborhood that caters to visitors with pets. As in any major city, the pet laws here can be hit or miss, depending on the neighborhood you're staying in.
Typically, pet-friendly neighborhoods will have one or more parks nearby, where dogs (and maybe even cats) can roam. You'll also want to make sure the hotel you are staying at explicitly mentions that your pet is allowed to stay with you.