Thanks Jörg. Having done some more investigation, it seems that if I also want GSM in Colombia I'll need to go for the PLS8-US.

I'm not sure how many people this will be useful to but here is a breakdown of PLS8 modem/operator support in Colombia. I've tried to figure it out as best as I can but official information on some of them is scarce so don't blame me if I've made a mistake.

Notes:

Une operates on the Tigo network for 2G and 3G.
ETB, Uff! and Móvil Éxito operate on the Tigo network for 2G, 3G and 4G.
Virgin Mobile operates on the Movistar network for 2G and 3G.
DirecTV offers LTE only for the home which means no 2G or 3G and no voice at all until the roll-out of VoLTE (which is held back globally due to lack of QoS guarantee).
Although Tigo and Une have merged, it's unclear whether they have unified LTE services to support both bands. Tigo will or have already relinquished the 50MHz block of spectrum in the 2500MHz band.

PLS8-E

Claro: GSM No, UMTS Yes, LTE Yes
Movistar: GSM No, UMTS Yes, LTE No
Tigo: GSM No, UMTS No, LTE No
Une: GSM No, UMTS No, LTE Yes
ETB: GSM No, UMTS No, LTE No
DirecTV: GSM No, UMTS No, LTE Yes
Avantel: GSM No, UMTS ???, LTE No
Virgin Mobile: GSM No, UMTS Yes, LTE No
Uff!: GSM No, UMTS No, LTE No
Móvil Éxito: GSM No, UMTS No, LTE No

PLS8-US

Claro: GSM Yes, UMTS Yes, LTE No
Movistar: GSM Yes, UMTS Yes, LTE Yes
Tigo: GSM Yes, UMTS Yes, LTE Yes
Une: GSM Yes, UMTS Yes, LTE No
ETB: GSM Yes, UMTS Yes, LTE Yes
DirecTV: GSM No, UMTS No, LTE No
Avantel: GSM Yes, UMTS ???, LTE Yes
Virgin Mobile: GSM Yes, UMTS Yes, LTE No
Uff!: GSM Yes, UMTS Yes, LTE Yes
Móvil Éxito: GSM Yes, UMTS Yes, LTE Yes

Official sources:
http://www.claro.com.co/wps/portal/c...s/movil/4g-lte
http://descubre.movistar.co/4GLTE/que_es.html
https://compras.tigo.com.co/promo_4g
https://www.avantel.co/cobertura/4g-lte.html
http://www.uffmovil.com/cobertura
https://www.virginmobile.co/web/virg...cios/cobertura

Third-party sources (some have conflicting information):
http://www.worldtimezone.com/4g.html
http://www.nemesisla.com/descargas/f...as_moviles.pdf
https://www.samsung.com/co/pdf/LTE.pdf
http://www.4gamericas.org/files/9714...ina_4.1.15.pdf
http://www.4gltemall.com/blog/4g-lte...m-in-colombia/
http://www.telecompaper.com/news/etb...ombia--1041633
http://www.lte-tdd.org/news/ind/2014-10-08/4558.html
http://www.gsmarena.com/network-band...untry=COLOMBIA
http://wiki.apnchanger.org/Colombia
http://www.budde.com.au/Research/Col...-Analysis.html
http://www.virgin.com/news/virgin-mo...-colombia-2012
http://www.lte-tdd.org/news/ind/2015-05-05/6187.html
https://www.telegeography.com/produc...m-post-merger/