Summarize the following:
Check online to see if there are any guinea pigs in rescues or shelters in your area. You can search the websites of your local shelters or you can use general pet adoption websites, such as Petfinder.com. You can also look on the Guinea Pig Adoption Network for adoptable guinea pigs in your area. If you don't see any adoptable guinea pigs on your local shelter's website, don't assume they don't have any. Many shelters do not list their guinea pigs and other "exotics" for adoption online. However, beware of back yard breeders who sometimes post there. They will usually have numerous babies and will usually charge more than $20 re-homing fee for babies. Healthy, perfectly social Guinea pigs are frequently being rehomed on Craigslist at no fault of their own. Many backyard breeders breed solely for money and looks with little to no regard to health, longevity, or temperament of the animals they are producing. Pet stores and backyard breeders are notorious for selling sick, parasite-infected guinea pigs. Pet stores usually get their guinea pigs from pet mills that are like puppy mills for smaller animals. This is why they often get sick animals in stock. If you want to get your guinea pig from a breeder be sure to thoroughly check them out beforehand. Do online research on them. Make sure they are breeding their pigs ethically and with the animals best interest in mind. It's best to visit several breeders before choosing one. Pick the breeder that you feel most confident in.

Summary:
Consider adopting an adult guinea pig from a rescue or shelter. Call around to local shelters and ask if they have any guinea pigs for adoption. Look in your local newspaper for classifieds or online classified websites, such as Craigslist, for guinea pigs to adopt. Avoid bad breeding situations.