Should locals be involved in social and economic monitoring?

I am in Belize for 7 weeks where my masters project objective is to help a local NGO design a practical and locally-relevant system for monitoring the social and economic impacts of their work. This NGO does both conservation work to protect a corridor it owns, and community work to improve the livelihoods of the local people and train them to farm in more environmentally sensitive ways.
The first challenge that I’ve come up against is an unexpected one: the communities are apparently skeptical of this NGO (and indeed all other NGOs in the region) and may be unwilling to take part in defining what social and economic factors we should be measuring.

From our point of view, understanding what works and what doesn’t should enable the NGO to improve the assistance it gives to the farmers, thus improving the situation for the farmers. Although I haven’t had the conversation with them yet, my colleagues here think that communities will see this as a waste of their time – they only want to be involved if they see tangible benefits to them.

The interesting thing is that all the documents I’ve read about participatory socio-economic monitoring make it sound like the communities really wanted to get involved, were interested in spending time doing it and put up no resistance.

Is that the case in most places?

How do we convince the communities that they should help us decide what to monitor? (Or should they?)

How can we get them involved? Do we need to pay for their time?