In the 10 years that we've been timesharing, the only time we've had a problem with being pestered was in 2000 at Westgate's Town Center in Orlando. Other than that they've left us alone for the most part once we've checked in. At check in it's really simple, just tell them no. You don't need to do anything more than that or build some sort of fancy strategy to avoid the salesmen.
As for unplugging the phone I've never done that. In all the exchanges we've done, only that one time at Westgate would it have done us any good. I suspect that it was Westgates phoney maintenance meeting (really a sales presentation) that got people to unplugging phones. In fact, not having the phone plugged in if there were an emergancy siutation at the resort could be dangerous since the front desk couldn't reach you without coming to your room.
Having said all of this every resort we've stayed at, including the resorts we own, have called and left messages daily on the voice messaging service. But it hasn't been about sales. It's been the daily activities or about maintenance issues such as pool/hot tub closings, weather/beach/surf conditions or any special events they have planned (ice cream social, resort welcome breakfast, owners informal update meetings {Marrriot does wine and cheese informal get togethers with the resort management team, not the sales team}). It has never been a problem with except for that one time back in 2000.
So go and enjoy your vacation. Tell them know at check in and get your parking pass. Leave your phone plugged in and just check/erase the messages daily. I've never found it to be as bad out there as what some of the others feel that it is.