I have recently used two Latam travel vouchers that I had received for different inconveniences experienced during the past year.

While I was technically unable to employ them online during the booking process (as described in one of the previous posts) - I had even tried different itineraries and fare classes - there was no problem in using them via phone with their Customer Service.
They had actually encouraged me to do so and call once I had my trip set up and flights selected, as the non-functionality on the website seems to be a known issue. Important to mention that because of that inconvenience, Latam honoured the same price as if I had reserved online and I was able to burn both vouchers (together worth around USD 420 or so) in one go, just indicating their respective numbers (which always start with LA's 045 code, at least if ex LAN stock).

So, basically your cheap trip to one of the many Zika-free places in the LATAM territory is just one phone call away. I would definitely recommend not to let this opportunity go, nor to cash in the voucher, as this would most probably not imply the same value as offered for a flight purchase.