I live just 30 miles away and go to Newport on a regular basis. Never had an issue as described. What has changed from all I can tell recently is that there is parking set up for motorcycle's only and there is no charge for it. Cars parked right across the street from the bikes are paying via meters or up to $20.00 for a spot. Yep, there are signs as you roll into Newport about loud pipes. I have V&H Ovals on my 05 Ultra, not loud and probably no EPA stamp??? Not sure, never looked. The other thing that has changed is some of the pubs (West Deck) that used to allow bikes to park in front of them can't any longer (it's a fire lane now) so you have to pay to park down there. And yes, quite a few of the lots do turn away bikes but I've found that to be when you are closer to the free bike parking areas. Down by the West Deck area they will be happy to sell you a spot for $20.00 and let you put 2 or three bikes in it. Just my .02
Joe