Reddit mentions of Practice Makes Perfect Spanish Verb Tenses, Second Edition (Practice Makes Perfect Series)

Don't have any PDF links for you, but I will say RE: Rosetta Stone...

You can get many of the same resources for free on Duolingo. But it depends what kind of Spanish`you want to learn. For example, if it's Iberian Spanish (Castellano, Spanish Spanish) then duolingo might not be such a safe bet because the Spanish on there is based mostly on the Latin American dialects.

If it's physical books you're into, this is my bible. I have found it so comprehensive and it fills in some gaps nicely. But perhaps also get this to give you a nice grounding in the grammar and syntax.

One thing you should definitely focus on is verb tenses. This is an excellent workbook I've used in the past. It will summarize all the different tenses and force you to use them. It will also introduce some new vocabulary for you so you will want a Spanish dictionary handy.

Some college-level texts are also recommended here, but they might be more detailed than you need. I believe the general placement tests are generally easier than the CLEP (which I am taking), but they are usually geared to high school students with at least a few semesters under their belt.

I'm not certain what kind of textbooks you can get a hold of in Ecuador, so how about online resources? There are a lot of websites that are very useful in providing you with a good general overview and start to Spanish grammar.

Check these out:
Studyspanish.com is quite good as a first grammar guide. Very concise, and not overwhelming.
Spanishdict.com is a really good online Spanish dictionary. They also have grammar videos/exercises, which I linked to you here.

In my opinion, don't worry much about perfecting grammar from the get-go. Read these grammar guides so you could get somewhat of an idea of how Spanish sentences are constructed, but don't be hard on yourself if you can't remember everything. As you read and immerse yourself more in the language, you'll slowly get a better idea of the grammatical structures in Spanish. Cliche, but it'll take time.

I highly recommend the Learning Spanish Like Crazy audiobook. Start it right after you get through the Study Spanish grammar guide. It teaches you practical Spanish that you can use right away in your everyday conversations. It's really really good! There's also volume 2 and volume 3 for when you complete the first volume.

As you're working through that, you could consider working on this verb workbook at the same time (I believe there are free downloads online), and also Duolingo for exercises in verbs, grammar, and vocab.

Afterwards, maybe check out Verbling for free Spanish classes online that you can join and for finding more conversation partners.

To practise listening, you can download podcasts from iTunes. I found Coffee Time Spanish to be a good one. There's also Extr@, which is a series aimed towards beginners. Turn on the subs and follow along. The acting is pretty ridiculous in the beginning, but it does give you some confidence when you find that you understand everything. The only thing with this is that they use Spanish from Spain, so the accent is different from those of South American countries.

You're not in school (at least as a student haha) so don't feel confined to textbooks and having to do everything the traditional classroom way! Language-learning should be a fun and enjoyable process, and there are a lot of different ways to do it. Also, conversing with native speakers is indeed currently your most valuable resource. Since you're there, take advantage! Talk to people in Spanish using whatever you know/learn that day. Every learner is a beginner at some point, so don't be afraid.

Looking forward to the intermediate-level-resources-seeking post. :) Good luck!

Couple of books that are working for me
Accion Gramatica

Spanish Among Amigos

Spanish Verb Tenses