Yes, but we'd need to understand the degree that they need cleaning... although I was very surprised recently of how much dirt came out of my seats that 'looked' clean.
303 are good products but I am convinced that the best cleaning for carpets and cloth uphostery is EXTRACTION. Some of the other (e.g. foam and spray) cleaners would have you believe they will bring dirt to the surface where it can be vacuumed away - perhaps true in part, but I think some of them just ground in the dirt and add soap residuals besides. Perform a good cleaning and rinse using extraction and you will see the dirt that comes out and you will notice the difference in the appearance.
I have a Bissel 2x Proheat for the house that works very well in the ride as well. Just used it 3-4 weeks ago doing the spring detail. There are many other extractors out there and you can do a great job with cleaners, water and a wet/dry vacuum. It doesn't need to be expensive and fancy to be good and efficient.
I did use 303 fabric guard last summer - I guess it works okay, but it really stunk up the inside for quite some time - so if you go there, expect to leave it open for a couple of days to dry and air out.