About ¼ or a fourth of the way, you can stop at Glen Avon, CA. This is about 13 minutes west of Riverside.
About ⅓ or a third of the way, you can stop at Champagne, CA. This is about 19 minutes west of Riverside.
About ⅔ or two thirds of the way, you can stop at West Covina, CA. This is almost an hour west of Riverside, or about half an hour east of Los Angeles.
About ¾ or three fourths of the way, you can stop at El Monte, CA. This is almost an hour west of Riverside, or about 17 minutes east of Los Angeles.
If you drive straight through without stopping at all, the total distance is 58 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 1 hour, 2 minutes.