Argentina and Chile
 

This will be our first time in South America.
We are looking for authentic experiences: trekking, kayaking, photography. We will be flying wherever possible and take public transit (long distance bus) if needed
Proposed itinerary:
NA - EZE, stay for the day to rest
EZE - USH - 5 days
by bus to Punta Arenas, Puerto Natales and El Calafat 7 days
PUQ - PMC - 4 days exploring the area, undecided what to do, where to go
PMC - SCL, 3 days
SCL - EZE, 3 days
EZE - IGR, 3 days
crossing over into Uruguay for 4 days
Is it worth spending time in both SCL and EZE - maybe shorten the time in each city?
Are there any "must do's/see's in the areas we are visiting.
Any other comments and insights are appreciated.

Regarding Chile, in the Puerto Montt area you have lots of beautiful options. You can go to Puerto Varas, Frutillar, Lago todos los Santos (Petrohue and Peulla), hike in Cochamo or visit Chiloe island. Considering you have just 4 days I would not go to the city of Puerto Montt and, clearly, choose some of the options I gave you.
While in Santiago, you should go to the city of Valparaiso and spend 1 night there. 2 nights in santiago is fine, and if you dont like big cities, you can hike in the Andes near santiago (cerro manquehue is the easiest, but there are others like cerro pochoco or cerro el Plomo).
I hope this helps.

I love Buenos Aires and could spend weeks in that city. All people I met have said that they took too short time there. A week is a good start. Alot of nice arcitecture, restaurants, clubs and people.

I second this, it is a Flyertalk firm favourite. Get a rental car from Pueto Montt airport, drive to Puerto Varas. Next day drive to Petrohue, drive up Volcán Osorno, have a hot chocolate. Drive back down, have a leisurely driver around Lago Llanquihue until you reach Frutillar, have tea and cake, drive back to Puerto Varas

That leaves you 2 spare days, I would honestly be inclined to stay in Puerto Varas, maybe a drive along the coast a bit.

Ancud on Chiloe is a place where I have had happy times, to really push it you can probably make it to Valdivia for a night but Ruta 5 tolls are not as cheap as they used to be. I love Valdivia, a trip to Niebla is a favourite, a boat ride around the rivers, a trip to the Kunstmann brewery, decent restaurants. According to Google Maps, Ancud is about the same time-wise as Valdivia, I would probably pick the latter.

If you have to choose, I'd choose Chiloe (head down to Castro or points south) over Valdivia. I also advise not to drive over the back side (North/East) of Lago LLanquihue. The road is unpaved (unless there have been recent improvements) and precarious in spots. The other rides (out to Petrohue, and as far as Pto. Octay on the north side of the lake, is fine. Pto. Montt to Pto. Varas is only about 15 minutes on a nice highway, so even if you don't stay in Pto. Varas (which is very scenic, but very sleepy), you'll be there quickly. I've had many a tasty lunch @ Angelmó (in Pto. Montt) - I just have them make a mixed seafood plate.

If you're spending three days at the Falls, you probably want to go to the Brazilian side too (nice walk, including the "mist", plus I liked the Bird Park near the park entrance for hundreds of free flying big tropical birds in a walk through aviary. I wasn't able to go, but I wish I had been able to see the big hydroelectric power plant near the three way border with Uruguay, which you apparently access from the Brazil side.

The bad news is that (for USA citizens) Brazil requires an advance visa, which is a $160 hassle plus visa service agency fees.

(1) There are no visa service agency fees if you do it yourself; and
(2) Effective Sunday, Brazil offers U.S. Passport holders an electronic visa.

Question for experienced Travelers to Chile:

Arriving by ship at Punta Arenas tomorrow, first of four Chilean ports. Final disembarkation happens at San Antonio.

Ship passes out note to all passengers saying absolutely no food allowed into Chile, along with confusing Chilean form that makes Global Entry kiosk food declaration items seem like chikd’s play. Asked for clarification, ship gives contradictory messages, the last of which is that packaged food is allowed.

Can i disembarark in San Antonio with Argentinian wine and candies, without risking incarceration in a Chilean jail?

Many thanks!

Yes you can. I've never arrived by ship, but just declare that you have these items. I've been admonished just once (for a permitted item - ground coffee) that I needed to have declared it, but no fine. They are serious, and I wouldn't be surprised if you'll be greeted by cute little agriculture doggies upon arrival. Their noses are well-refined.

Apologies for taking so long to acknowledge appreciation for the responses. They are very valuable.
Renting a car was not in our plans, but it sounds like we need to look into it.
Great forum, thank you.