Your yeast will dictate what temperature range it will ferment best at. It can still ferment outside of that range. I don't know what yeast you're using, but low 60's should be fine. As others mentioned, you will have a slower fermentation but most people actually prefer it to be slow. The biggest thing you want to watch out for, is sudden changes in temperature. If you have a thermal blanket (or even a normal blanket) you can wrap your carboy as a precautionary measure. This will help as your house changes temperature throughout the day. Another thing you can do (if your kitchen is clean) is to keep it near the back of your refrigerator.