Well, the average daily high temp in San Cristobal de las Casas in Dec is 70 F. The OP said: "it would be nice to be in a place that was in the low 60s."

But is certainly does get cold at night, and last time I visited I needed to escape to Comitan de Dominguez for some warmer weather.

No don't recall spotting the bus but then again wasn't looking out for it. I think we spent 2 nights in Taroudant and it was just okay being really just another city type of destination. Much preferred Imlil, Tafroute, Dades, Todra etc.

If it was nearer yes but I don't foresee a return to Morocco simply because it's long way from the other side of the world :)

...... bus fares cost between 50 and 70Mad. (euro 5.- 6.50). ...see links below for schedules and fares...

Most bus-lines plying the route ... https://www.lagare.ma/en/trajet-agadir-essaouira_aller_2019-07-19.html

The two premier lines are... http://www.oncf.ma/ and http://www.ctm.ma/

Buses depart the Gare Routiere located about one kilometre east of Place Salam at the round-about junction with Ave. Mohamed V., passing Souk al Had (walled market) a busy and noticeable place, the Gare Routiere is a little farther-on on the south-side of the road. City-bus L2 passes, L12 and L22 pass nearby.! https://www.alsa.ma/agadir/lignes

Map showing Souk al Had and the Gare... https://www.google.com/maps/place/Station+road+travelers+Agadir/@30.413732,-9.5725107,16z/data=!4m5!3m4!1s0x0:0xde857e8778618144!8m2!3d30.4163782!4d-9.5657408

There is a small hostel in Air Mansour, called Auberge Ait Mansour. Look for them on Facebook. The owner, Abdou, speaks perfect english, and can probably give you great advice how to get there from Tafroute. We had a car, so I can't be that helpful. But we liked Tafroute much better than Tarroundant for hiking. There are a few places in Tafroute where you can get a bike..it would be a bit of a trip to bike there but I'm not a biker. If you stop at the Hotel Les Amandiers (the only fancy hotel) you can get lots of information from the owner about hiking the area. You can also get a beer! We just sort of set off and were lost most of the time so I can't give great information, but villagers were friendly when they weren't hiding from us and it is a beautiful area to base yourself. We slept at Hotel Tafrout which seems fancy but was actually inexpensive, and ate every meal at Cafe Restaurant Tangier, which also has rooms. I don't think you can get to Tafroute from M'hamid in one day, in fact I'm sure you probably cannot. You might have better transportation options going out of your way up on N10 rather than N12, although N12 is more direct. If you do take N12, when we stopped in Foum Zguid (because it was dark) the one simple guest house in town was closed. We had to stay at an expensive resort about 5km east...it was nice though.

Nice places, villages and little towns I know for one or two nights can be Rosenheim, Bad Tölz, Wolfratshausen, Dietramszell, Tutzing or in a 200 km distance near the lake Bodensee Wangen, Isny, Kempten, Lindau (the old part), Meersburg, Ravensburg. Nearly all of them have connection from/to Munich by train or bus.

..... in Agadir on Rue la Plage facing the promenade and the Atlantic, find Restaurant Le Flore, maybe 300mt. south of the Marina, in March just walk in for a terrific food experience.
https://agadir.madeinmedina.com/fr/restaurant-le-flore-10286.html

Don't visit the 'Port Restaurants' except to have a look, a cluster of eating places originally for workers in the Port, touts 'fish' for tourists nearby at the northern-end of the beach and promenade.... its a bit of a scam, uncomfortably noisy and poor value, its not authentic, partly contrived for tourists while locals eat here too, there's a double pricing system.... one for locals and another for tourists.

From Taroudannt consider a visit to the Oasis Village Tioute, about an hour away on the Sous Plain, this village where water rises from underground streams creating a small green small-holding family farming complex supporting a village of a hundred or more people and a two teacher primary school. On a large rocky hill dominating the surrounding low plain a fortified Casbah overlooks the valley with good views, a bit of a climb.
Some days boys with donkeys for hire offer to guide visitors around the Oasis, they'er not needed as the area is small and some of it isn't accessible, fenced-off to prevent the afore mentioned donkeys eating the crops.

From the north-gate of Taroudannt about 12 kilometres the village of Tamaloukte marks the edge of the southern slops of the High Atlas Mountains.
https://www.google.ie/maps/@30.5420068,-8.8642395,12z

This a lovely area to explore, there's a river running behind the village, to cross-over on foot is a stepping-stone experience, in March be careful if the river is in spate with Spring rains, only cross the river with local advice and a slack-flow of water.! Cars are driven across this ford, trucks more frequently. In March here the fields and mountains are a riot of colour with blossoms.

If in Taroudannt over the week-end days the town is filled with farmers and their children from the surrounding valley and hills, street entertainers perform mostly on the historic Place Assrag, the town buzzes with excitement. For a flavour of Taroudannt see this older post ......

https://www.lonelyplanet.com/thorntree/forums/africa/morocco/easter-and-itinerary?page=1#post_22435986

Very nice hotel in a quiet area just on the other side of the small bridge facing Old Hanoi, (where there are no hotels) ; NGO HOUSE VILLA. In the countryside between Hoi An and An Bon,g Beach / VILLA LOAN. Both will cetainly give discount for long stay (or she rents a house)

If you're keen to go for some warmth I'd head south, the north can be chilly and rainy at this time of year!

As Tim mentioned, you've got some lovely towns in the south, Sidi Ifni is far nicer than Essouria ... and to add to his list, I adore Tiznit! You can easily get to Inezgane from Marrakech (where Agadir bound buses arrive) and continue south from there. Not sure of how long it takes these days with the autoroute, I drove it last December in about 3.5h, previously used a bus before the autoroute was finished & it was a long slog of 6-7h!

My Kiwi godson had previously been to a variety of Asian cities, spoke French, but wasn't prepared for the madness that is Marrakech!!! Beware!

Bonne route!

Kira