Is it possible to use 1 mil.translucent
polyethylene sheeting to protect plants from
frost or freeze in early spring?

Plastic isn't a good choice -- it may actually increase
frost damage. You might look at something like row cover --
here's a couple of sources I've found reliable:

http://www.groworganic.com/maincat/n/0067.html
http://superseeds.com/products.php?cat=19

You want the cover to completely extend to the ground.

Kay