There is nothing in Islam against checking each other out for the purpose of marriage , there are many ahadees according to which Holy Prophet(SAW) asked his sahaba if they have seen or met their future spouse.
Masjis is supposed to center of all attention and all activities of Muslim life. In fact Masjid is the best place to allow it because all the Chaperons are around so no hanky panky other than checking each other out can happen. It is the safest place to check someone for the intention of marrying someone.
If you go to Masjid for praying then nothing should stop you from going there.
