Tobefair, a seven-year-old gelding, has won his last seven races.
He was gifted as a colt to Michael Cole three years ago, in return for looking after two fillies on his farm.
Unable to afford the training costs on his own, he decided to offer 50% of the ownership to people he knew through his local pub, the Cresselly Arms at Cresswell Quay.
The syndicate grew to 17 members but none except Mr Cole had owned a racehorse before.
They said they were amazed when Tobefair started winning races and never dreamed he would make it to Cheltenham.
The festival runs from Tuesday to Friday and culminates in the showpiece contest, the Gold Cup.
Mr Cole said: "There's a lot of these big people now, they've got 40, 50, 60 horses, and it doesn't mean anything. But it means something to us."
Syndicate member Andy Pannell described the experience as "total exhilaration", adding: "We were stood on the steps at Newbury and I thought I was going to have a heart attack. My heart was pounding, thumping."
This is also a first appearance at the Cheltenham Festival for Tobefair's trainers Debra and Paul Hamer's, whose yard is at Nantycaws near Carmarthen.
At least two bus loads of supporters will be travelling from the Cresselly Arms to Cheltenham for Tobefair's race, the Pertemps Final Handicap Hurdle, on Thursday.
But syndicate member Jennifer Cole said they have only one real wish: "Win or lose, just get him round the track and bring the boy home."

The photos showing militants rigging the temple with explosives and a large explosion were circulated by the jihadist group's supporters.
Syrian officials and activists said on Sunday that it had been blown up.
The UN's cultural organisation said the deliberate destruction of Syria's cultural heritage was a war crime.
Unesco's director-general, Irina Bokova, accused IS of seeking to "deprive the Syrian people of its knowledge, its identity and history".
She also expressed outrage at the beheading last week of Khaled al-Asaad, the retired chief archaeologist at Palmyra, who refused to co-operate with IS.
The Temple of Baalshamin was built nearly 2,000 years ago and was considered the second most important structure at Palmyra - the monumental ruins of a great city that was one of the most important cultural centres of the ancient world.
Syria's director of antiquities, Maamoun Abdul Karim, said IS militants had packed the Graeco-Roman temple with large quantities of explosives and detonated them on Sunday, bringing down the inner sanctum, or cella, and surrounding pillars.
Three of the images published online on Tuesday appear to show men placing barrels of explosives connected with detonating cord around the temple's interior and on several exterior columns.
Another image shows a large explosion and plume of smoke, and a fifth shows the aftermath, with piles of rubble where the temple used to be.
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One caption reads: "The complete destruction of the pagan Baalshamin temple."
The images could not be independently verified, but they carried a logo IS often uses for propaganda from Palmyra, which the group captured from Syrian government forces in May.
The Syrian Observatory for Human Rights, a UK-based group that monitors the conflict in Syria, reported that the temple was destroyed a month ago.
IS has ransacked and demolished several similar ancient sites that pre-date Islam in Iraq, seeing them as symbols of "idolatry".
Until the temple was brought down, they had only demolished a statue of a lion from Palmyra, though they used the site's theatre to stage the public execution by children of more than 20 captured Syrian army soldiers.
A racehorse owned by a syndicate from Pembrokeshire is a favourite to win at this year's Cheltenham Festival.
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Islamic State (IS) has published images of what appears to be the destruction of the Temple of Baalshamin at the ancient ruins of Palmyra in Syria.