What is the ruling on sending Salaams to the Prophet of Allah Sallallahu Alahi Wasalam with those who are going to the blessed City of Madinah?
Answer:
It is the belief of the mainstream Ahle Sunnah Wal Jamaah that all the Prophets including our beloved Messenger Rasulullah 
are alive in their graves.
Imam Baihaqi 
has narrated a hadith of by Saaiduna Anas Bin Malik 
that the prophets are alive in their graves praying.
With regards to your question, it is permissible to convey someone’s Salaams to the Prophet of Allah . After reciting ones own Salaams, one should convey the Salaams of that person (who had requested him to do so), in the following way:
“Salaam upon you, O Rasulullah! From … (Mention the name of the person). He seeks your intercession by your Rabb” (Imam Shurunbulali in his Nurul Idah p.192)
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham