From additional research I have clarified this answer to better reflect the documentation from Spanish Historians who have provided much more detailed commentary and record of the events of the Grenadian War.
Your initial question asks if the Grenadian people believed that the Spanish would be faithful to the terms of the surrender. The Spanish Wikipedia article references Luis María de Lojendio in his historical chronicle Gonzalo de Córdoba (p. 90), and has this to say about the negotiations:
Las últimas negociaciones secretas incluyeron el respeto a la religión islámica de los que decidieran quedarse, la posibilidad de emigrar, una exención fiscal por tres años y un perdón general por los delitos cometidos durante la guerra.
Which I have roughly translated with the assistance of Google Translate to:
The last secret negotiations included respect for the Islamic religion of those choosing to stay, the possibility of emigrating, a tax exemption for three years and a general pardon for the crimes committed during the war.
It is clear that the terms of the surrender where secret only to the signing parties. Which had later consequence as the Grenadians found out..
Antoni Simón Tarrés a modern Spanish Historian published La Monarquía de los Reyes Católicos a chronicle on The monarchy of the Catholic Kings (page 56). His work is referenced later in the Wikipedia article mentioned above, in which we can glimpse the reaction the Grenadian people had to the terms their leader had handed them over unto.
El 25 de noviembre de 1491 fueron firmadas las Capitulaciones de Granada, que concedieron además un plazo de dos meses para la rendición. No hubo necesidad de agotarlo, porque los rumores difundidos entre el pueblo granadino de lo pactado causaron tumultos, sofocados tanto por los cristianos como por los fieles a Boabdil, que acabó por entregar Granada el 2 de enero de 1492
Which I have roughly translated to with the assistance of Google Translate:
On November 25, 1491 the Treaty of Granada was signed, which also granted a period of two months (for the Grenadians) to surrender. There was no need to exhaust it, because rumors spread among the Grenadian people of the agreement caused riots, stifled by both Christians and the faithful to Boabdil, which eventually gave Granada over on the January 2, 1492
Rioting in this case, is a direct result of the Treaties signing. So it is evident that a group of the Muslim Residents of Grenada had no trust in the Spanish to Maintain the treaty.