My Evangalical neighbors said to me that Jews will not go to heaven because they don’t believe in Jesus Christ. They were referring to John 14:6. I personally believe they are the chosen people and Jesus says further on in John 14:11 that the Father and he are one. So if you believe in the Father that will suffice.
Your neighbors have an incorrect understanding of the requirements of salvation, but you also have an incorrect understanding of trinitarian theology. See the links below for information on the salvation question. As for the trinitarian question, the Father, Son, and Holy Spirit are the one, true God, yes; but they are three distinct persons. Deliberately refusing to believe in the Son when you have reason to believe that you should is indeed grave matter, and belief in the Father (or the Holy Spirit) alone does not alter that. The key though is a deliberate refusal to accept revealed truth. If a person is innocently ignorant of Christian truth or innocently incapable of accepting it, God will not punish him for innocent ignorance or innocent error.