Praise be to Allah.
If your permanent residence is in al-Jubayl, and you decided to do Hajj when you were in that city, then you must enter ihram from the miqaat, which is Qarn al-Manaazil (Wadi as-Sayl),because of the report narrated by al-Bukhaari (1524) and Muslim (1181) from Ibn ‘Abbaas (may Allah be pleased with him) who said: The Messenger of Allah (peace and blessings of Allah be upon him) defined the miqaat of the people of Madinah as Dhu’l-Hulayfah; that of the people of Shaam (Syria) as al-Juhfah; that of the people of Najd as Qarn al-Manaazil; and that of the people of Yemen as Yalamlam. And he said: “And these miqaats are for the people at those very places, and besides them for those who come through those places with the intention of performing Hajj and 'Umrah; and whoever is living within these boundaries can enter ihraam from the place he sets out, and the people of Makkah can start from Makkah.”
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked: A man from Jeddah is living in al-Jubayl and he wants to do Hajj tamattu‘ [doing ‘umrah and Hajj together, exiting ihram in between]. From where should he enter ihram for ‘umrah? Should he enter ihram from the miqat or from his family’s house in Jeddah? When the eighth day of Dhu’l-Hijjah comes, from where should he enter ihram for Hajj? Does he have to go back to the miqat and enter ihram from there?
He replied: If a man is from Jeddah but works in another city, such as al-Jubayl or Dhahran or Riyadh and so on, when he wants to perform Hajj, he should enter ihram for ‘umrah from the first miqat he passes through. Then when the eighth day [of Dhu’l-Hijjah] comes, he may enter ihram from Jeddah, and he does not have to go to the miqaat again, because the Prophet (blessings and peace of Allah be upon him) defined the miqaats and said: “…whoever is living within these boundaries can enter ihraam from the place he sets out, and the people of Makkah can start from Makkah.” So the answer to this question is that it is permissible for the questioner, when he has exited ihram of ‘umrah, to go to his family in Jeddah, then when the eighth day comes he may enter ihram with his family or by himself from Jeddah, and set out for Mina.
End quote from Majmoo‘ Fataawa Ibn ‘Uthaymeen (21/327).
He (may Allah have mercy on him) was also asked: There is a married man who lives with his wife and children in Riyadh, and his mother and father are in Jeddah. What is the ruling?
He replied: If he comes to Jeddah, then he is a traveler. Hence if he goes to his family to visit them and also intends to do ‘umrah, we say: you must enter ihram from the miqat, because your place of residence is Riyadh. As for Jeddah, it is the place of residence of his father and mother. Hence in Ramadan he may break his fast if he travels to where his father and mother live, as he is resident in another city.
End quote from Majmoo‘ Fataawa Ibn ‘Uthaymeen (21/329).
You have the choice between entering ihram for Hajj on its own (ifraad) and remaining in ihram until you exit ihram on the Day of Sacrifice, or entering ihram for ‘umrah with Hajj (tamattu‘), which is better and easier, because when you have completed your ‘umrah, you can exit your ihram, then when the eighth day of Dhu’l-Hijjah comes, you can enter ihram for Hajj from the place where you are staying in Makkah.
And Allah knows best.