Found the following article online, use it to answer the question: What indigenous group was Alvarado fighting for Atiquipaque?

In Guazacapán, now a municipality in Santa Rosa, Pedro de Alvardo described his encounter with people who were neither Maya nor Pipil, speaking a different language altogether; these people were probably Xinca. At this point Alvarado's force consisted of 250 Spanish infantry accompanied by 6,000 indigenous allies, mostly Kaqchikel and Cholutec. Alvarado and his army defeated and occupied the most important Xinca city, named as Atiquipaque, usually considered to be in the Taxisco area. The defending warriors were described by Alvarado as engaging in fierce hand-to-hand combat using spears, stakes and poisoned arrows. The battle took place on 26 May 1524 and resulted in a significant reduction of the Xinca population. Alvarado's army continued eastwards from Atiquipaque, seizing several more Xinca cities. Tacuilula feigned a peaceful reception only to unsuccessfully raise arms against the conquistadors within an hour of their arrival. Taxisco and Nancintla fell soon afterwards. Because Alvarado and his allies could not understand the Xinca language, Alvarado took extra precautions on the march eastward by strengthening his vanguard and rearguard with ten cavalry apiece. In spite of these precautions the baggage train was ambushed by a Xinca army soon after leaving Taxisco. Many indigenous allies were killed and most of the baggage was lost, including all the crossbows and ironwork for the horses. This was a serious setback and Alvarado camped his army in Nancintla for eight days, during which time he sent two expeditions against the attacking army. Jorge de Alvarado led the first attempt with thirty to forty cavalry and although they routed the enemy they were unable to retrieve any of the lost baggage, much of which had been destroyed by the Xinca for use as trophies. Pedro de Portocarrero led the second attempt with a large infantry detachment but was unable to engage with the enemy due to the difficult mountain terrain, so returned to Nancintla. Alvarado sent out Xinca messengers to make contact with the...

Xinca