Walker partners fellow new boy James Thomas at half back, while Smith joins Cardiff captain Shaun Powell in the centre.
Powell is demanding more of his side this campaign after last season's disappointing finish.
"I'm an ambitious player so I'm targeting every game we play. It's a good starting block against Llandovery so hopefully we'll push on from there," he said.
"For Cardiff RFC eighth last season wasn't good enough and we've got to improve on that and we should be pushing for the top three at least.
"Our defence in pre-season is looking really strong and we've covered all areas really."
The Drovers completed the double over the Blue and Blacks last season as they went on to finish fourth and the home side will be looking for revenge this time out.
In the front five Cardiff include Cardiff Blues signing Campese Ma'afu as well as two other new Blue & Blacks, Aaron Fowler and Callum Lewis.
Cardiff XV against Llandovery:
15 Joe Griffin 14 Matt Smith 13 Richard Smith 12 Shaun Powell (c) 11 Steve Cullen 10 James Thomas 9 Alex Walker 8 Dan Crimmins 7 Ellis Jenkins 6 Reuben Tucker 5 Dan Partridge 4 Matthew Screech 3 Callum Lewis 2 Aaron Fowler 1 Campese Ma'afu.
Replacements: Ethan Lewis, Lewis Smout, Rhys James, James Murphy, Thomas Young, Sion Hopkins, Max Woodward.