It is actually really old, some of the buildings from the 1800’s still stand, but many are new and keep to that style. Obviously many of the old buildings needed rennovations over the year, perhaps they made them look too new. From my research that you inspired, it turns out that lots of places burned down back in those days and the fire department was not as effective in those days, since it consisted of people with buckets.
To summarize, old town was moved to it’s current location in 1880 because the railroad came through there, prior to that is had been a bout 3 miles east. I think the bank (which is now a mexican restraunt named the bank), a hotel, a store and a few other places are original from 1880. The pre-1880 store is still in place but that’s about it for the pre 1880 town, it’s just not near what people know as old town. The map of old town in 1884 is pretty much the same as it is today, street names and such are the same http://www.temeculahistoricalsociety.org/temecula.html
One of the reasons it existed was that it had water and was on the stagecoach route from the east to San Francisco. They would change horses here, many stages did not go to san diego or even L.A., in those days San Fran was the big city. When the railroads replaced the stages, the shops moved to the r/r stop, which is where it still is today.
Another little known fact, it was part of San Diego county until 1893.
The short answer, shortimer, is yes, sorry to tell you, but you are kinda wrong, it really is an old town and was one of the few towns on the map of so cal in the 1800’s.