Thank You everyone for all your help.

Turns out my friend just had a huge garter snake and probably some other snakes, but no rattlers were found.

According to a fish & game guy, baby snakes don't show up until September and rattlers don't get that big. There have been rattlesnake sightings reported by the police and on the news, so it's possible one's hanging around there.

They're probably hiding in all the tall weeds, under rocks and in gopher holes. My friends said they weed whacked all around the garden, made a lot of noise and basically did what you said, cleaned up.

Thanks everyone. It was fun.