i thought it was 35 pesos...but i could be wrong...but i certainly dont remember paying over 40.
getting the expresso bus is a MUST tho!! If your spanish is not good...just ask for Parque Indepencia. Make sure the guys who run the station put you on the right bus...as the bus drivers themselves will just try to get you to get on.
now..what I need to figure out...is which guagua to take to get you to the main station to catch the guagua back to boca chica. I hate paying a taxi the extra money!