I'm fairly new to the forum as well, but have been collecting information on Tulum for a few months now. Welcome!
We started out by emailing a bunch of wedding coordinators in advance of a site visit trip. One particular coordinator, Angelina (Angie) Cardenas, stood out to us. We initially found her through Tulum Weddings Destination. She is the onsite coordinator for Las Ranitas Eco Boutique Hotel as well, so has a lot of strong Tulum connections. She met us at the airport in January and showed us around the entire Mayan Riviera for 2.5 days along with her friend and fellow independent coordinator Nallely Tamayo Ruiz. We were in love with Tulum, but had tasked them with finding us an old style hacienda for the ceremony. We *almost* booked a gorgeous hacienda in Cancun, but it turned out to be cost-prohibitive, so we were happy to stick with the original plan.
In Tulum, we checked out:
Ak'iin Beach Club
Ana y Jose Beach Club
(I'm working on a full review of these venues, but until then, I hope this gives you a place to start.)
Our top choices were Las Ranitas and Ak'iin. Las Ranitas was too expensive and Ak'iin came close to meeting our budget. The big surprise was Ana y Jose, as they came in under budget. (For a great thread on Ana y Jose, check here: http://www.bestdestinationwedding.com/t/34669/ana-y-jose-tulum-brides-post-here. San Fran Sara offers tons of great information.) Unfortunately, after signing a contract, we waited almost a month and never received a counter-signed contract or info on making a deposit. Our coordinators told us counter-signed contracts are not customary in Mexico, but we didn't feel comfortable without one, nor did we feel comfortable about the lack of communication from their onsite coordinator for three and a half weeks. After we decided to pull out, Ana y Jose's owner Jackie offered to personally look after our wedding to make sure there were no other missteps, but it felt too risky. Angie and Nallely then told us that Las Ranitas had still not booked a wedding for our date, which is only seven months away, so we were able to negotiate a contract, sign, and put down a deposit within 24 hours. So in the end, we got our first choice! And there is a certain peace of mind that comes with working directly with a coordinator at the venue.
One thing to note about coordinators (based on the advice on the forum and our own personal experience), communication is quick and regular in the beginning, seems to slow down considerably in the "in-between months," then picks back up about a month out. If you're used to internet-addicted, constantly-connected folks like I am in the San Francisco Bay Area, it can be frustrating, especially when planning from so far away. The other thing we've noticed is a lack of attention to detail from almost everyone we've communicated with, from coordinators to venues to vendors. Mistakes in dates, email addresses, email attachments, calculations (on budgets) ... all really important details, at least to me. The exception, far and away, has been del Sol Photography.
I fell in love with del Sol through their posts on this forum (as evidenced above :-)), their website, and communicating with their Sales + PR Concierge, Ael Enciso. They were also mentioned on the blog of my favorite local photographer, which was a plus, because I really wanted to choose vendors who are local to the Mayan Riviera. Ael has been enthusiastic, kind, informative, thorough, and generous with her time. I never wait more than 24 hours for a response, and all my concerns are handled with understanding and care. When I thought we couldn't afford del Sol, Ael offered me the brilliant suggestion of putting photography on our registry, but also referred me to a handful of excellent other choices that might be able to match our needs. I thought that was classy and professional. Ultimately, we reworked our budget and went back to del Sol. Thank goodness they were still available for our date. This decision was the easiest of them all.
As for other vendors, our coordinators have recommended The Makeup Pros (they seem to be popular here on the forum but wayyy out of our budget/priorities), flowers (not really our style), and a guitarist (we haven't looked into this yet -- too busy trying to book a venue!).
Hope this helps!