ANSWER:

They must not go to the masjid to pray in congregation after eating onions and garlic, because the angels would be offended by its smell. 

They can pray at home, the validity of salah is not effected by this.

 

Is salah acceptable when prayed after eating onion n garlic? i have heard a hadith (interpretation of d meaning):muhammad pbuh said whoever eats onion and garlic,should not even pass by our masjids.