Chis and Fleas

Do you take your chihuahua outside or do they get any outdoor activity? Mine were constantly indoor guys but my hubby finally made a closed in porch right in front so they could go outside when the weather is nice and enjoy the breeze. I think it's wonderful and so do they but I also believe that the outside freely-running cats in the neighborhood have contributed to our flea problem. I recently purchased a bag of "bug out" for my lawn and hopefully it will work. I think that you must treat fleas indoors and outdoors if your chis are outside any at all. What do you use when using a flea control method? What works for your chis?