Mars' thin atmosphere and lack of magnetosphere exposes its surface to lots of Solar UV radiation and cosmic radiation. But Mars also has some dramatic altitude gradients in for example Valles Marinaris. Are there any areas which in this way are protected from A) Solar UV radiation and flares and coronal mass ejections, and/or B) substantially protected from cosmic radiation?
If you want protection from radiation on Mars, you'd have to either live in caves, or else build some kind of thick dome overhead, or live behind thick walls/ceiling. Cosmic radiation will reach you anyway as long as the sky is visible, so deep valleys can only help you so much.
The only way to stop hard radiation is to place a lot of "stuff" (thick mass) between you and the source. A pile of dirt would suffice in many cases. The geologic layers on top of a cave would work well. I guess a dome could also work if it's thick enough. Habitats with thick ceilings (and walls) could also be an option. Have a large water reservoir? Put it on the roof of the habitat: voila, instant radiation shield.
The main concern is the stuff coming in from directly overhead; near horizon even Mars' atmosphere is thick enough to reduce radiation a little. So prioritize the ceiling.
I guess at the base of a hill with some overhang above your head you'd get some shielding, but again - is the sky visible? That's the main concern. Also, areas under an overhang may or may not be safe (stable) long term.
Find a very large boulder (the size of a house or bigger), much taller than your habitat, and place the habitat right next to it - you've cut 50% of radiation right there.
For a shorter term stay, a simple habitat with thin panels would be enough - not very different from the interplanetary vehicle after all.