hi, I'm a guy who writes from Italy. in july i should be in california for a tour of california and parks like yellowstone, etc. I was looking for a Californian travel agency that can offer a group tour to locations such as those described below:

Los Angeles, Grand Canyon, Antelope Canyon, Monument Valley, Arches, Bryce, Las Vegas, Death Valley, Yosemite, San Francisco

an Francisco / Yosemite / Death Valley / Las Vegas / Bryce Canyon / Capitol Reef / Canyonlands / Moab / Monument Valley / Horseshoe Bend / Antelope Canyon / Grand Canyon / Palm Springs / Los Angeles

Can anyone from the forum give me some indication?
thank you

Here is a similar question about tours of the national parks in Utah where you may find some useful information. It lists some companies that offer tours and you can check out those website to see if they have something that matches your interests.

For the parks in Utah and AZ you may have better luck finding a tour that starts and ends in Las Vegas.

Can someone recommend a tour company for National Parks in Utah

Look at orbridge.com as they have offered tours of U.S. National Parks in the past. They are not based in California but are located in the state of Washington, north of California. They organize trips all over the world and are a very high quality company.