I truly doubt garlic works for fleas, and since its safety is questionable, why try it? Fleas are a terrible problem for people and pets as well. They can take up residence in your carpet and jump on your ankles and bite. Don't get that started.
I assume hoosieroriginal does not want to give her pet the commercially offered products such as Advantage, Frontline, etc. I understand completely. I did not want to do this either but knew how horrible and miserable fleas can be. I finally settled on Comfortis. It only works for fleas, but we don't have a problem with ticks, and heartworm is rare here. I chose it because of the National Resources Defense Council's rating, linked below.
http://www.simplesteps.org/greenpaws-products
There is other helpful flea fighting information there.
I also believe that choosing a product which has been around for quite a number of years is a good approach.
Last year I was able to skip the Comfortis for several months in the winter, but this winter for us has been often in the 70-80+ degree range, so I believe fleas are still a risk and continued the Comfortis, so far.
Dogs and cats can still live long, happy lives even though they are on flea products.