Taxi Rates

Have always found taxi drivers in Zihuatanejo shady to say the least. The system in Huatulco much more transparent and honest. Rates are actually posted on street signs. Having said that, we prefer Zihuatanejo and will just choose to walk more to avoid the crooks and the hassle of negotiating

Not my experience for the most part.
I don't often take taxis. I like and prefer to walk as much as I can.
But when I do take taxis, usually from Soriano or Sam's Club back to Madera/KauKan, it's usually a non-event.
Perhaps the fact that I know the fare (although I don't always know about official or 'unofficial' increases) helps.
Also some cab drivers think the top of Madera ('KauKan') is Madera and others think it is La Ropa, may lead to a difference of opinion of about 5-10 pesos. I usually go with the flow- do I have the correct change for the fare and the tip...or is change necessitated. Fumbling for change can be seen as a sport activity...