South Lake Tahoe is an amazing place to go hiking on the cheap. They have forested lands that you can hike for free. Just make sure to grab a free tag at the start of the trails and fill it out. Put the tear off label on your backpack. In my entire time hiking there I have yet to see anyone check, but why risk a ticket when the permit is free. There are also a multitude of primitive and nonprimitive campsites where you can enjoy nature and pay little to nothing for the privilege of camping.
TThe great thing about Lake Tahoe is that the air is clean compared to Fresno and due to the slight elevation you can get even more of a workout. When plan your trip all you need is hiking shoes and a swimsuit. There is a multitude of lakes you can enjoy swimming in. If you go to the Fallen Lake Camping area you are near at least a dozen hiking trails. The trails are extremely well marked so you most likely will not get lost. Additionally you can see the Stanford camp or the lake from many areas so that can give you a visual guide even if you do get lost.
Some of the best trails for great views include the Rubicon Trail which is an approximately 3-5 mile hike that goes up and down the shoreline of Lake Tahoe and then winds around through the mountains and drops you off at Vikingsholm Castle. Another great hike is the Mt Tallac Trail which starts off as a very easy hike but as you continue upward gives you a descent glut workout. It takes you past the Floating Island and the Cathedral Lake. It also includes some stairs carved into the mountain which are just amazing. Another fabulous areas is the Desolation Wilderness area which has thousands and thousands of acres worth of trails many of which are well labeled. If you want a true hiking and endurance adventure you can try the Tahoe Rim Trail. This hiking trail is approximately 165 miles lone. The hiking trail goes along the ridge and gives amazing views of the lake from huge elevations with many areas of unobstructed views.