All perfect praise be to Allah, the Lord of the Worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
If you want to go to Mecca after your return, then perhaps you want to perform ‘Umrah, or perhaps you simply want to perform prayer at Al-Masjid Al-Haraam. If your intention is to perform ‘Umrah, then you should assume ihram (ritual consecration) before crossing the miqat (place for assuming ihram); each place has its own miqat that is well-known to the people. However, if you want to enter Mecca, not intending thereby to perform ‘Umrah, but merely to perform prayer at Al-Masjid Al-Haraam, then there is no need to assume ihram at the miqat because ihram is necessary only for those who perform Hajj or ‘Umrah. Instead, you should perform much prayer and tawaf (circumambulation), given their great reward. The Prophet, sallallaahu ‘alayhi wa sallam, said: "... these mawaaqeet (plural of miqat) are for the people at those very places and for those who come through those places with the intention of performing Hajj and ‘Umrah..." [Al-Bukhari] You do not hold the intention of performing Hajj or ‘Umrah (so there is no need to assume ihram).
Allah Knows best.