I used to ignore all calls (except those from my young daughter) when out with a client. I don't anymore. Clients today want immediate results to inquiries. I check my email every five minutes from my TREO and answer every call. I don't stay on the phone longer than taking the general information and promising to get back to the caller as soon as possible. As long as the client gets an answer, they are satisfied. In my area, I can be out with a buyer for several hours showing a few homes on Lake Lanier - and callers will move right on to the next name if I don't answer. I excuse myself from my client and never make them feel like they are not my priority. On the other end, my clients know that they can always reach me when they have a question.
I think it's all in the approach we take to our business and the manner in which we conduct ourselves when with our clients.