Good thing tarantulas don't spin webs across your bike trail. They would really freak you out. They can get several inches in size. I've very rarely found them in the desert where I live. When it is mating time, that's the best time to see them in rural areas.
If you ever happen to be on the U of WI Madison campus look at some of the buildings along the lake like the Limnology lab. The spiders hanging from the building are pretty, well fed from lake insects, and numerous. Definitely not for those who fear spiders. I used to regularly find black widow spiders in my landscaping adjacent to the house. You can always tell a black widow web because it is disorganized, not the geometric webs spun by most spiders. They are very common in the desert.