I've never had that problem in Los Angeles. I think, at least at LAX, if you tried that boarding-all-zones number it might constitute a safety risk.
I've certainly experienced it at other airports, however, and it's deeply frustrating when they don't pre-board. I see the problem a lot more in the East than in the West, probably because the East employees know how stupid the America West boarding system is and don't follow it at all.
The America West system works well in theory, but it's so different from other systems that it confuses the average joe.
The big problem with the system are the families and parties greater than 1. You've got people seated next to each other who have different zone numbers. We all know that you board all together with the lowest zone number of your party, right? WRONG. No one knows this. It's absolutely essential that the gate agents make some sort of announcement explaining the process every time they board an aircraft.
In Phoenix, I heard one lady who said the following:
"At US Airways, we board by zones. Everyone please take a look at your boarding pass and confirm your Zone Numbers. Don't be afraid if your neighbor isn't in the same zone. Your party may board with the LOWEST Zone number in your party." She sat there and made everyone look at their pass, explained to them exactly how they are going to board, and calmed any feelings of panic they might have had. That was perfect. Everyone "got it."
The problem is that, explaining this mess of a boarding process every time wastes time. In the time it takes for them to do it, they could have boarded the plane by rows. There is NO time saved because this method's alleged efficiency is contingent upon everyone knowing how it works up front. US Airways does a piss-poor job of informing people of how their bizarre boarding procedures work and, as a result, you have what we have now: chaos at every gate.
US Airways has done everything they can to eliminate frequent flyers. They're now dealing with a less-experienced, less-sophisticated, and generally less-intelligent crowd. This is what they've been salivating over...plane after plane filled with KETTLES. It's here.
At this point, I think it's time for US to abandon the zones and board the planes by the rows...back to front, with Preferred, First Class, and Active Duty Military having pre-board privilege. It works for everyone else.