If you are looking for XianQi in a Chinese American establishment try asking for JungGi. This pronunciation is by the way almost identical to the name of Korean Chess, JungGi (pronounced JungGee).
Ya, If you are in chinatown, you'd better pronounce it like Cantonese..-JungGi or JungGee.
OR, You can just say "Chinese Chess." Some people will know what do you mean.
It seems like a lot of Chinese American in chinatown speak Cantonese not Mandarin. When I first came to San Francisco I thought I can speak Mandarin in chinatown but the truth is-- Some Chinese there they can only understand Cantonese. (Not English or Mandarin..)