No experience in a Mooney 252, but I've got about 300 hours flying a M20J and owning one in a co-ownership for about 9 years. Currently have it up for sale as life has taken us in different directions. Personally, I'm in the middle of a career change to become a professional pilot and flight instructing right now to build hours.
Great airplane and many fun family trips in it. The J will do about 140-150 knots true airspeed sipping 8-9 GPH. While not the middle of the Rockies, I've done a few trips from Houston to west Texas and a trip to Page, AZ and my M20J did great crossing that terrain.