How to get there?
From Bogota: by bus - Bogota - Oiba (or Barbosa, then Barbosa - Oiba) - aprox 5 hours bus trip for 30.000 COP (10 EUR), from Oiba - Guadalupe by minivan, it is really adventurous ;) - aprox 50 mins, 6500 COP (2 EUR). The last bus to Guadalupe leaves around 5pm.
From Bucaramanga or San Gil: by bus, aprox 3.5-4 hours.
There are a few accomodation in Guadalupe, the price for a private room is around 40 000 COP (13 EUR)/night/2 pax. You can book your accomdation upon arrival - weekends usually are crowdy.
There is no season, so you can visit this amazing place throughout the year.
I would highly recommend you Jose, a local tour guide who shows you all of the hided spots and he loves telling stories about the zone. Jose also has a restaurant and a clean hostal with private rooms in the village - the breakfast is really delicious - fresh juice, coffee, omlette, arepa for around 8000 COP (2,6 EUR).
You can check also here:
http://yourcolombia.com/quebrada-las-gachas/