Thanks to all of you for your comments. Since I asked for the feedback so late and was committed, my husband, my 18 year old son and I ended up staying for six nights at Marble Arch. Perhaps we are naive but we found the location interesting, not the least bit concerning, and the hotel staff very helpful (except the front door guy!) We frequently walked in the surrounding area during the evening hours (from Marble Arch back to the hotel) and ate at several neighborhood establishments like the Aussie owned pub. Not one suspicious person or event.
The bartending staff and the concierge(s) were exceptionally nice and helpful. There was a good mix of nationalities staying at this hotel which, again, we found interesting.
The hotel is in the middle of renovating and our room was up-to-date, clean with re-done bath, the best bedding, etc. The only hassle was they gave us one king with a cot...son adapted, but we couldn't negiotiate a larger room without paying alot extra. The view wasn't good but we didn't spend much time in the room.
Again, thank for taking your time to respond.