You don’t have to have a website to sign up to Google+ Places you just need to be a business.
Claiming your Google+ Place is the second most important thing you can do to improve your online presence. Google+ Places was Google Local, this is the mini listing you have based on Google maps. The screen shot below is a Google map result for the word dentist in my town of Phoenix. Every red dot is a dentist.
Google has every dentist in town on the map even though at least half do not have a web page and most of them have not claimed their Place.