My muslim wife's mother is leading a homosexual lifestyle, is it hallal or haram to stay at her house in the US while visiting there?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Homosexuality is an evil thing and it is contradictory to the sound Fitrah (natural disposition upon which Allaah created mankind); for more benefit in this regard, please refer to Fataawa 88137 and 86547.

If you have no evidence that your mother-in-law is practising lesbianism, then you are not permitted to accuse her of doing so. However, if you fear that she may negatively affect your wife and children in regard to their religion and moral conduct, then you should not reside with her, especially with the presence of this strange woman. As regards visiting her for a limited period, then this is something tolerable, but you should be careful not to leave your children in seclusion with her lest she might affect them in a bad way.