BashfulDwarf, from my observations it exists to some degree throughout the Costa Rican culture but is perhaps more pronounced when the person is less educated or when they are in a more stressful environment such as the Gulch provides. We gringos experience the lying by the girls in the Gulch since that is who we are most around, but the expats living in Costa Rica can tell you the lying is equal among Ticas and Ticos, and it's not just lying to Gringos; they lie equally to each other. Personal authenticity that we value as gringos is just not as important to Ticas and Ticos as is conflict avoidance and Pura Vida.
A basic tenet in the CR culture is conflict avoidance. A small example is when asking for directions. We gringos prefer the person to say they don't know instead of giving us directions when they know the directions they are giving are likely wrong. It's about saving face while wanting to "appear" to be helpful. Ticos feel compelled to try to help even if they have no clue where you are trying to go. Form and process are more important than actual results. We goal oriented gringos tend to see it just the opposite.
Another example is delivery of your purchases. Manana does not mean tomorrow. It means not today. So, what a gringo sees as a delivery appointment scheduled for 1:00PM on Tuesday, the Tico frequently sees it as just a plan to make the delivery sometime soon and the gringo ranting and raving only causes the Tico to delay even further to avoid the potential face-to-face conflict with the gringo. Pura Vida!
We gringos respond to a lie with "What?!? Do you think I'm stupid?" Just know that Ticas and Ticos view being lied to as a minor inconvenience that is much less than the person not making the effort to lie when they know the truth will cause the teller and the recipient to feel angry, disrespected or to lose face. Even though I think I understand it, I'm still frustrated when it happens to me.