They never, ever had that option. The only downtown option that they had was north of where you are talking about. It would have had to have been artificial turf and off site parking, and after the BS that Skip Rimza pulled with the Tempe site the Cards weren't about to go in that direction.
I am probably not nearly as up to speed on this situation as you are... But, I can recall them discussing the potential of a site located south of Chase Field and south of the railroad tracks...
The whole west valley excuse is BS anyway. How far is it from New York to East Rutherford on game day? A good 30 min or more drive. What about the folks on Long Island or the Connecticut burbs? Do you think the 49ers are worried about moving to Santa Clara, CA?
No... it's not BS. It's definitely an issue. Would be less of an issue if there were other things going on, other reasons to be out there. Other draws... and most importantly, other ways to get there - like Light Rail.
As for your East Rutherford comment - first, you need to separate Giants fans from Jets fans.
As for Giants fans, the vast majority live in New Jersey. So when the Giants are playing, the stadium is mostly filled with people from New Jersey. Sure, there are some that come from NYC, Long Island and like me, from Connecticut. However, that comprises a small fraction of the fan attendance.
The Jets are a totally different matter... They have a much smaller fan base in New Jersey as they came to New Jersey after the Giants.
And here is where the issue I raised about legacy fanhood and the problem that the valley deals with more than any other major sports town, comes to light.
You simply can't compare a New York pro sports team to a team in the valley. For both the Jets and Giants, you are talking about fans that literally go back decades upon decades... Franchises who have been entrenched in families for generations. My story is the prototypical New York fan story, where from the very first memory I have of sports, it was that of my family (Uncles, Aunts, Grandparents, Cousins) all demonstrating their passionate, faithful fandom for the Giants/Yankees/Knicks/Rangers. As a non-NY sports fan, it's impossible for you or anyone else to fully grasp the true gravity and depth of this experience. You grow up believing that sports ONLY exists in NY. You believe that there is truth and a god-given right to the superiority of NY teams and their players! And most importantly, you simply HAD NO CHOICE. There were NO other options. You were either a rabid fan of a NY team, or, you were not a sports fan, period. Between family and friends, believe me when I say that there were repercussions if you even came close to uttering a favorable comment about a non-NY team.
So, back to Jets fans... Their Super Bowl win in '69 created a fan base that lasts into today... A fan base that will travel from NYC/Long Island and Connecticut (a commute that with traffic is often more than an hour)...
The Giants have 2 Super Bowl wins and loads of amazing playoff history.
The Cards have none of this...Will it come one day? I hope so... however, at best those days are decades away...