I was out at the airport today and picked up a brochure for the shuttle to La Paz.. The shuttle is a modern 54 passenger bus that runs direct to La Paz malecon. Shuttle operates daily. Their website is: shuttletolapaz.com. The price is 325 pesos p/p one way.
Depart SJD @ 14:30, arrive in La Paz @ 17:30
Depart SJD @ 17:00, arrive in La Paz @ 20:00
Depart La Paz @ 7:00, arrive at SJD @ 10:00
Depart La Paz @ 9:00, arrive at SJD @ 12:00