I agree -- go in person to a dealership rather than send a formal letter. I understand you want to send a letter because you want them to know you’re a serious buyer, ready to purchase if they give you terms you like, and you don’t want to waste your time. They’ll be able to tell that from your visit. Plus by visiting, you get the benefit of (a) seeing if you like the CA and (b) test driving the car.
For those not in a hurry, I recommend you do as I did, and test drive a ton of cars of different makes and models over the course of weeks. I had a blast and now I know just how much better my Bimmer is than other cars in its class.
