I was just in Cabo (mid July) and rented through Avis for about $30/day. I think there are decent weekly rental rates as well. I thought Avis was very professional and not as shady as some of the others can be.
In general, if you are staying in the Corridor, you'll definitely want to rent a car. (We didn't take insurance, but many people recommend it - I think it was $12/day). As taxi rates are stupid high in Cabo, the car is very, very convenient. San Lucas has good parking for cheap (10 or 20 pesos) at the large mall located on the left, lower side of the harbor as you enter from the highway. In addition, you may want to visit San Jose which is easy to navigate via car.
In addition, there is a Walmart and Sam's Club on your way into Los Cabos (on right, large complex - you'll see it). Very good prices and good place to stock up on essentials (read: rum) instead of paying ridiculous resort prices.
I really enjoyed having my own transportation - very easy to drive in the area - and you get to know the towns much better.
As a final comment, you can either take the new toll roads to/from the airport or the free regular "highway" (several lights). We took both and there was no noticeable difference, although locals indicated sometimes the regular highway can have traffic at certain times of day.
Go for the car and $15 insurance per day. You'll end up saving a lot in the long-run with your own car and will be free to drive up to any small towns on a whim.