I am considering buying a refurbished canon 60D and a Tamron AF 28-300 F/3.5-6.3XR lens. I take a lot of scenery but also fast action photography-dragracing etc. Is this a wise choice considering AF point sensitivity, etc.?
For 'fast action photography' - I'd imagine you'd want something with the 'ultra sonic' focus - its much faster than the old motors in lenses. If you're stuck to Canon, that means 'USM' lens. For 3rd party lenses, it means 'HSM' for Sigma and 'USD' for Tamron.
Unless you need that extreme 28-300mm range, I'd also consider something with a faster aperture and probably sharper. Each of the brands (Canon, Sigma, and Tamron) for that camera produce a 70-300mm f/4-5.6 that would also certainly produce better images. If budget is less of a concern - try a 70-200mm f/2.8, but I believe they're probably out of your price range. Addionally, a faster aperture than 6.3 is going to give your autofocus more light to work with.
If you're not stuck to Canon, consider a Nikon D5100 or D7000 or a Pentax K-r or K-5 and similar lenses as suggested above. Brand choice is really a whole other matter and is discussed in other questions (and here and here).