Yep, a Garter Snake just catching some morning rays to warm up. They feed on insects in your mulch, small lizards or a small mouse if it could find one. Harmless to humans, would never even strike unless cornered. His presence means you have a nice eco-system going on in your garden.
Black Racers shun humans and will usually put a rapid distance from one if so encountered. A beneficial snake like the Garter Snake. I have Coach Whip snakes in my garden, in the Black Racer family.
They don't hurt your crotons - not worse than scale.
Ricky - if you could train the Garter Snake to eat croton scale and then sucessfully breed them, you would attain $$$.