I've read some people put hardware cloth (wire mesh) in the bottom of the planter so critters can't dig holes and get into your plants.

I live in Arizona and I have 2 pallet beds, I toiled the ground soil then laid down weed cloth. I then laid the beds atop that. Just make sure if you trying to make an organic Garden Bed you do not use some sealants or stains on your wood. it can seep into the soil. I'm having great luck with Red Fingerling potatoes, Solar Boy Tomatoes and Mild Jalepeno. . Good luck, I'd love to see how it's going. I've also included a link to a Lady who is amazing! She has her degree in Urban Horticulture from ASU and is a practicing Horticulturist. Her page is awesome and VERy informative for desert gardening and landscaping.

Here is a link that might be useful: AZ Plant Lady

Yes, keeping the gophers out is a problem in Las Vegas so hardware cloth is pretty strongly recommended (I think the half inch mesh). Additionally co-lining with landscape cloth can repress weeds and grasses from coming up from the bottom.

http://www.unce.unr.edu/publications/files/ho/2010/fs1033.pdf

Here is a link that might be useful: Since you live in Vegas

Fun! Let us know what you do and how it works out! I prefer cinder blocks/wall blocks/bricks for raised beds here, but only because they seem to need less maintenance than wood. Either would be fine and if you start with wood and it falls apart eventually you could replace with wood or blocks. We'd love updates, so keep us posted! Happy gardening! Grant

Here is a link that might be useful: Pics from my garden, so far, May 2014