Opening up your aperture will definitely create the softness (DOF, bokeh, background blur) that makes for nice portraiture, but remember that it will let a ton more light in. In direct sun like the shots above, you'll need a super-fast shutter speed, even at ISO 100... faster than the 1/250s that your camera can synch with an external flash.
I love my 50mm f/1.4, but I don't get to use it as often as I like because I cant always get far away enough from my subject when shooting indoors. I think I'm going to add a 28mm prime to my bag very soon.

I'm pretty new to all this stuff myself, but I'm finding that good lighting starts to become formulaic or instinctive after a while (I can pretty much guess what my light meter is going to say before I test the flashes) and then from there, you can start getting creative with it.
The hardest part about shooting "models" for me is the posing. I've shot girls who actually model, and they just know what to do in front of the camera and they respond well to direction. Pretty girls in real life often get awkward when it comes time to get in front of the camera.
At the end of the day, it's still fun!

There is actually a way to sync the flash faster than 1/250. It's a setting in some cameras have called FP (Focal Plane). There are drawbacks and it's only usefull in certain situtations however. That's why reflectors are so great for situtations like this, no need to worry about sync speeds.

...and shooting with anything under 50mm for portraits distorts faces way too much (makes them look fat :p).

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go to your camera's flash sync setting and select "FP" or high speed sync. Check your manual, since it varies. On Canon's, I think it might even be on the flash itself. It basically tells the flash to cover the front & rear curtain duration. The drawback is you need more light by using more power and/or a larger aperture. You lose about 1 stop or more depending on shutter speed. The flash fires more "burst" in fractions of a second creating an almost continuous beam. It drains batteries, but most cameras/flashes revert back to normal mode if you stay below the max sync speed of 1/250 for most cameras.