May Allah accept all your good deeds and give you strength to remain firm and steadfast on the path of Islam. Aameen
Normally, all mosques are established for the purpose of providing a place of worship for Muslims and provide Islamic education for Muslims unless a mosque is built for another purpose which may be apparent from their attitude and activities taking place therein.
If a mosque is established and maintained by people who believe and practice mainstream Islam (The true teachings of Quran and Sunnah of the Prophet) then there is not reason to stay away from such a Mosque. However, if a Mosque is established and maintained by such people who have strayed away from the mainstream of Islam then one must stay away from such centers as the case with mosques or centers established by Ahmadis/Qadiaynis/Shias etc...
You can learn about the beliefs and practices of founders by going through their policies/statements etc...
It is always important to be in the company of righteous and trustworthy people.
If you would like to know specifically about some authentic centers and mosques in an area, you may ask us about it and we will do our best to assist you Insha'allah.
And Allah knows best.
Mufti Ikram ul Haq
Fatwa Center of America
27 Muharram 1432/ January 2 2011