Most pest repellents work for short periods of time at best. Remember your applying chemicals near or on something your going to perhaps eat. So I would steer clear of them. A good quality net and fence system is really the best method of preventing critters. They do make auto hose spray systems that work with deer for a short period of time until they figure out its not hurting them. Squirrels are a bit harder to stop as they can get around pretty much any type of fence you install. Live traps work well with relocation for them.

Woodbridge hit it on the head: most repellents do little to deter animals. A fence or trap/relocate are most effective.

Scent-based repellents will work for awhile on deer, if they are not too hungry. But you need to keep changing the product you use so they do not get used to the scent.