This has turned into a bit of a PoA fur-ball, so I'll keep it brief.
"What side of La Veta Pass do you fly on, Eastbound?"
If you answered "the middle" you need a Mountain Flying course.
If you don't know, go around the "long" way.
Hint: The prevailing wind will be out of the northwest. Visualize the air tumbling over rocks like water.
Since this will be in September and the Eastbound leg will probably be in the afternoon, I'll bet dinner when you get here that one of the no-go criteria will be met for even La Veta Pass.
Winds in excess of 15 knots In the rocks (And please check more than just the La Veta AWOS! It's shielded from some directions and is on the road, not at a mountain peak!), or brewing t-storms/convective activity in the Alamosa area. (And I mean brewing. Not partially developed. Not really building. The up/downdrafts of even small convective activity will be a problem if you're already at your service ceiling and have zero performance margin.)
The 170 is marginal on all but the coldest days. The Dutchess is probably below single-engine service ceiling when DA is factored in, depending on time of day. Most of us plan on being out of the mountains by noon on even good days. It gets pretty bumpy from solar heating up there in the afternoon.
Do I think "most pilots" can do La Veta? Yeah. Have I searched for those who didn't make it through there or turned out of the valley before Alamosa trying to out-climb the ridge to the East to avoid weather and lost? Yes. South face of Mt. Antero, that one. Took three crews worth of overflights to see it, and technical climbers to get to it.
That long pass with no "outs" is insanity. Just don't... on that one.
If the weather is perfect, La Veta is a nice little short-cut. Plan to be rocked (turbulence wise) just South of the large peaks to the north almost year-round, just a little, even if winds aloft at 12K MSL are below 15.
Keep an eagle eye on the ASI and VSI, they're your first indication (plus not being able to see over the ridgeline forward) that you're in a downdraft if you choose to go through it. Give yourself tons of room to turn around and be prepared to make a minimum airspeed, maximum performance *descending* turn because you won't be climbing or even holding altitude once you start it if you're using your escape route. Chandelles are close, but you're descending prior to the turn and the turn makes it worse.
All exterior lights on, crossing the pass. Plenty of near mid-airs in these natural "funnels" on a fair-weather day.
There's no recommended mountain frequency.
The recommendation is to give pass-crossing times to Denver Radio/FSS and Pireps so we know where to start looking for the aircraft pieces.
And file a VFR flight plan, please.
Now all that said, I'm with Ron and Alan but would feel remiss if I hadn't given some hints. I go the long way around myself when going West unless I know the weather is CAVU with virtually zero wind.
I honestly don't think you'll see "beginner" Mountain conditions in much of September in the afternoon. If you do, you'll enjoy the view coming over La Veta into PUB.
Watch out for the Restricted Areas on the West side of KCOS if you're going to turn northbound. They're hot quite often.
Since you're going to FTG, keep your head on a swivel and get on Flight Following around PUB so they'll hand you off to KCOS Class C. That corridor is busy busy.
Radar doesn't cover down into Alamosa on the West side. Weather info between KSAF and KALS in the valley is poor.
Note the locations of RCOs on your chart to talk to Denver FSS by the way. They're scattered around up there for reporting. The new AFSS folks don't have a clue about reporting in the mountains but try and teach 'em anyway. Wasn't a problem when the FSS was local... Sigh.
What else!? I'm sure that doesn't cover all of it, but there's some tips. If there's any weather or wind, go around. Please.
You don't want your obituary to read: "He picked a bad day for flying in the mountains."
Get lucky and hit a good day early, La Veta is pretty tame. Like all passes though, there's a point that you're completely committed. Crossing on a 45 is correct to a point, then you turn direct and boogie on over.
Don't be surprised if the turbulence gets worse and the downdrafts stringer on the East side if the wind is out of the West, which it almost always is.
I said it'd be short and then kept typing on my phone, if that gives you any indication of how much giving any advice and not being able to cover what a few hours with a Mountain CFI can cover, worries me. La Veta is pretty benign and I still typed all of the above. Monarch, Tincup, Hagerman, and a whole bunch of others are deadly more often than La Veta, but they all don't care about small aluminum craft being bashed into their rocks. If the wind is right, La Veta can create conditions and require climb rates that a light aircraft simply can't perform.
Treat it with deadly respect and hope for a beautiful no-wind day if you want to fly it. You can't quite see the pass from the ramp at KALS but almost. Don't be ashamed to turn tail and go back down-valley to KSAF either if things look squirrelly north of KALS. That's a long way to go back, so watch your fuel.
Enough said, kinda.
I've seen experienced mountain pilots say "Oh ****" and take their "out" more than once on days that looked perfect too...