Seems very strange to me that a car with so many on board cameras can’t read road signs when so many other (less technologically advanced) cars can!
Its only that the software in AP2 has not yet progressed to that point. Given the progress made on AP2 since its inception I don't think it will be long (and I expect red traffic lights and stop signs etc. recognition to arrive around the same time)
I have an older AP1 car and it has no trouble reading the speed signs (but not any other), including roadworks, motorway variable speed limits, etc. and changes speed the moment I pass a limit sign entering a 30MPH village ... provided it isn't obscured by a vehicle etc. so there is definitely a case for map-based data too - in particular jumping on the brakes as it comes into a 30 MPH zone is not brilliant, slowing down before then would be better / more legal! FWIW my AP1 will also slow down for a sign on the A1 which reads "In 2 miles (50)" which is not brilliant for any non-AP1-Tesla following me!!
But you are right that you should not be being sold a car that is under development without knowing all that jazz ...
... my only consolingly input is that the updates you get during the lifetime of the car will transform it from what you purchased. In the nearly-2-years I've had mind Tesla have added:
Summon
Auto park
Ability of car to brake when the car two-in-front brakes (and car in front does not / slams into Car One! there's a YouTube of that very thing ...)
Huge improvement to AP
and loads of bits and pieces ... Sound Graphic Equaliser went from 3-sliders to 5 and whilst not critical of course its a good example of all the small things, and there is talk about AP NOT driving in another car's blindspot.
Coming imminently are new maps with better route planning and crowd-shared traffic re-routing, similar to Waze, which probably the salesman didn't know about, nor tell you ...
This is how Musk does business I'm afraid. I have not bought the Powerwall because I want to be able to charge it up on E7 overnight, and the "time of use" software is seriously delayed (supposedly rolling out now, but I read some people saying "not be, yet" so I'm still on the fence). Once bitten ...
You will, of course, have forgotten about the speed limit sign recognition some months after you get that update ... whether it is "right" that the company didn't feel the need to tell you before you bought the car ... I'm not so sure.