How big is your print? If it is 4x6 then there are no more than 2MP in the picture. The print also loses a lot of information that is in the negative. It seems also that the first shot was out of focus and was underexposed (although it looks light). Scan from a 4x6 print is never be as good as picture from a 3MP camera.
1. A lot of mini-labs make lousy prints. Between old chemistry and operators who don't care, the results can be awful. Bring your negatives to another lab and bring one of your bad prints. Ask if they can do better. You may have to shop around to find a lab (and even an individual who works at the lab) who gives a darn. You may have to pay more for quality & experience.
2. A lot of mini-labs make lousy negatives. While it less common to mess up the developing machinery, it's not unheard of. But if you shop around, again you might find a lab who cares. (Scratches and dust are more common problems.)
3. Light leaks as mentioned. This may not affect all exposures equally. The ones that spent the least time in the leak area (e.g. end of the roll where you rewound shortly afterwards) might still be OK.
4. Take more control by developing, printing (or - gasp - scanning) your negatives yourself. If you can't find a lab you can trust, then learn to do it yourself. Details of scanning are off-topic (see hybridphoto.com) but every step you do yourself means you know exactly how well (or poorly) it will be done.
Concentrate on the Pentax, for now. Get a tripod and a cable release. Find out where you can get some fresh Ektachrome 100 or Fuji Provia 100F and get it processed (just developed, not cut and mounted). Quit trying to take landscapes. Take something reasonably close without any sky in it, preferably with lots of detail like a street scene.
I think you have light leaks in the Minolta and, probably, exposure issues. These are aggravated by trying to take pictures that appear to involve a lot of atmospheric haze and exceeding the film's exposure latitude by trying to combine sky and terrain using an averaged meter reading and no compensation.
Your Minolta has a fresnel focusing screen in the center for fine focusing and it should be clear when you are focusing on your subject. It also has a split image which should be aligned to indicate proper focusing. I am not familiar with the Pentax, but, hopefully, it is similar. Use a tripod and a cable release to allow you to focus precisely and not disturb the camera when you release the shutter. Bracket the shots to give the same aperture and three different shutter speeds for each, one at the metered speed, one one stop slower and another one stop faster.
If you cannot use slide film, use black and white. Use C-41 process B&W film if that is all you can get processed, but leave the color negative film alone for now. What you want to do is eliminate as many processing problems as possible and make any such problems as obvious as possible. Slide film is better for this because the exposure latitude is narrower, the color and contrast are not subject to problems in printing and metering errors show up faster. However, trying to take the kinds of photographs you are now with slide film and no compensation will just aggravate your problems.
If you can, get a light meter that reads incident light. If there is a large difference between it and what your camera is reading, use the incident reading to set the aperture and shutter speed manually for the exposure. Last, keep the light behind you--no shooting into the sun.
cyberspider - I'm interested in seeing the results from your new rolls - make sure to keep us posted. I just started out with this myself not that long ago and yes there is a lot to learn and there can be a few essential purchases to make at the beginning (I purchased my Epson v500 negative scanner for MF film before I purchased my first MF camera.) Just remember: Photography is a BIG world and it's your mission to find what you enjoy most about it and what it can do for you as a business. Don't be unrealistic but please keep your hopes up - your results will come around in time as long as you have the interest and determination to stick with it.