There's a lot of exploring to be done over there. Not much to see at Tumco though, it's mainly just some holes in the ground, foundations and a few tanks. We took my wifes sister out there a few years back, it was a rainy year and the wildflowers were incredible. This year may be good for that as well, we've had a lot of rain the past two months:
(Sorry it's not an analog image...but does show the main Tumco site.)
If you have a jeep or other 4WD there are some more interesting old mining sites to be found - but they're not as easy to get to. The "Names" or "Graffiti Hills" on the other side of the Cargo Muchacho's is easy to get to and pretty interesting.
If you're up for some hiking and exploring there's a lot of neat stuff around there - I just wasn't very impressed by Tumco itself.