Looking for fun and local places to exercise can help you save money. However if you are planning on a hour or more drive it is critical to consider exactly what you want and if the drive is worth it.
The Millerton Lake Recreational area is a short drive from Fresno. That is the pro of this Fresno area site. Another benefit of this Fresno county site is that there is no fee for parking and approximately 10 miles of hiking that you can do here. The views of the lake in the Fresno County site are great. Additionally there are ample bathrooms and drinking fountains. Another benefit of this Fresno County area is that it is near many stores so if some in your group do not want to hike they can go shopping.
Now there are negatives. The largest negative is that hiking here feels like walking in an urban park at times. Some times of the year you may feel like you are walking or hiking in Fresno's Woodward Park. There are many people around and bicycles. Cars are visible from many areas of the trail so that is another negative as it takes away from the scenery. Additionally there is not much technical challenge with this site.