Is it a good idea to take pre natal vitamins even if you don't plan to get pregnant soon?

Absolutely. If soon is still sometime this year, prenatal vitamins will provide an excellent source of folic acid, which when taken before conception, can reduce the risk of congenital anomalies (neural tube defects) and miscarriage. If soon is years from now then they are still a good multivitamin, if you are looking for this type of supplement.