We spent most of our first full day in San Juan in
El Yunque (which is actually an hour or so outside of San Juan), the only tropical rain forest in the United States. It is in the U.S. National Forest system, and has an interesting arrangement where it is free to enter the forest but you pay to go in the visitor center. I imagine this makes the locals happy, seeing as how they already know where they're going, but it was pretty cheap anyway (only $3/adult) and well worth the time if you're bringing an 8-month old who is going to limit your ability to hike around and see stuff.
The reason I mention the visitor center at all is because it's the source of the first two pictures I've included here. To get to the entrance you walk across a catwalk that goes through the forest canopy, which is festooned with signs labeling it a wildlife viewing area (the walkway, not the canopy). It wasn't immediately obvious what wildlife we were supposed to be viewing, but then we saw this little guy walking along the railing:

I think this is an
Emerald Anole, although I didn't ask at the time and it didn't volunteer any taxonomic details. It was kind of an overcast day (more on that later), so the photo doesn't really show how incredibly bright green he was (and maybe still is... we've fallen out of touch since taking this picture).
Next, on the way back to our car we saw this crazily-colored tree trunk:

Given the way the bark was peeling off like paper leaving a smooth, shiny trunk it looks like some variant of eucalyptus, but the eucalyptus trees back home certainly don't look nearly as verdant. I'd be interested if anyone knows what kind of tree it is.
After leaving the visitor center we headed higher up the mountain ("El Yunque" is the name of the mountain in the center of the forest, but it's also used to refer to the whole forest) to have lunch at a picnic area and then take a short hike to
La Mina Falls. While we were eating lunch we were reminded why it's called a rain forest as the skies opened up and dumped on us for 10 minutes or so. The picnic tables were in very nice little pavilions set amongst the trees so we got to stay comfy and dry (except for the 100% tropical humidity) for the time being, but this was just a warning of things to come.
Our plan was to walk to the waterfall and go swimming in the pool at the bottom before heading back to the car, so Steph and I were already wearing bathing suits and we had towels with us. This ended up being rather fortunate, since the shower during lunch was not the end of the day's rainfall by any means. When we were passing by some of the picnic tables again (we had to go back to the car after lunch to leave the stroller and some extra stuff there before starting our hike) it started raining again, so we ducked into one of the pavilions to wait out the worst of it and better prepare Evan for the weather. The temperature dropped several degrees when it started raining, so we bundled him in pants and a jacket (he wasn't going to be doing any work on the hike to keep warm, after all), plus we cocooned him in our camp towel to keep him dry. Here we are in the pavilion, waiting for the rain to let up a bit:

As you can see, Evan seemed happy enough with this arrangement, although he liked it even more once we started moving again (Evan is not a fan of lollygagging on walks):

Here's one more picture from the pavilion, a self-portrait Steph took of the three of us. I wouldn't say our rain avoidance interlude is necessarily worth three pictures, but this may be the best arms-length backwards-camera self-portrait ever taken, and Steph deserves to be complemented for pulling it off:

Notice how well centered we are in the frame, and the wonderful composition... a truly remarkable accomplishment!
Anyway, we waited for 10 or 15 minutes while the rain got stronger and weaker, but it never really stopped. Eventually we decided to just press on and get wet. As it turns out the water above wasn't that big of a problem (we did get soaked, but we were planning on going swimming anyway), but the water below made things interesting. The trail sloped downwards the entire way with a bunch of stairs, and the rain made the stone very slippery at times. Add to that the extra 20+ pounds of baby and the difficulty seeing where I was putting my feet (because of said baby) and it made for a bit of a challenge. We were able to manage well enough, though, and after half an hour or so we arrived at the falls:

Since the temperature had cooled down with the rain and Evan seemed to be contemplating getting fussy we didn't go swimming after all, although you can see some other people couldn't pass up the chance. We stayed at the waterfall for a few minutes to take it all in, then headed back up the trail. As it turns out, climbing stairs with a BabyBjörn is a bit awkward since every time you raise your foot your thigh bumps into the baby's dangling legs... just so you know.
We'd hoped to do another short hike a little further up the mountain, but by the time we got back to the car Evan had made it quite clear that he was ready for a nap. So we buckled him into his car seat and spent the rest of the afternoon taking a driving tour of the rest of the forest and the surrounding area (a moving car isn't quite the soporific it used to be, but it often does the trick). We didn't see any other babies on our hike, though, so we still felt rather adventurous.