You don't always need riding shoes with the 105s or the speedplays. It helps a lot, but isn't required. You can use your regular shoes.

I use
[h=1]Shimano PD-M324 SPD Dual Platform Pedal[/h]and the 105s. You can adjust the tension and I have the tension being pretty low. With the M324s they automatically rotate to the SPD side so if I were to use the other wise then I have to flip them myself.

Edit: Once I started wearing clipless shoes I always wear them now, even for my 2 mile commute. Go with shoes with a recessed cleat though. You can always upgrade to a road shoe (and use your SPDs with them too; I did until I with with the SPD-SLs).