Sounds like a great time! C&C per req:
1. Excellent leading lines, but what do they lead to? You really need something for the eye to settle on 1/2 to 2/3 of the way into the image. Technically it's fine, but artisically, IMO, it's only half done.
2. Nice, but strikes me as a little under-exposed. I would try and brighten it up just a bit, at least enough to get some life in her eyes. Remember that there's a reason the vertical orientation is referred to as 'portrait'! As well, consider your background. This could have been a really great shot of an attractive young lady with the right background, but a street sign, bicycle rack etc... I'll bet all you would have had to do is turn a bit and you would have found a better background. Never by shy about asking people to move a little if it will improve the picture, or about moving yourself.
3. Very nice... almost. I've always realy like this sort of shot, but again, get that camera up on end. If you're shootng a long, thin, vertical subject, get your camera vertical. Think of how much stronger this would be if we could see the stem as far down as where that disjointed leaf attaches!
4. This one really just screams 'snapshot' to me. That's not necessarily a bad thing, but in this case I don't find much to recommend it. Her expression is rather odd, the background dark and distracting, and the horizontal orientation? Well... that's been mentioned.
Overall, they're a nice set of shots. If I may suggest something, spend a day shooting ONLY subjects which need a portrait orientation. Get yourself in the habit of using the camera both ways.
Just my $00.02 worth - your mileage may vary.
~John