What does it say about Spanish culture?

one thing id mention is Almodovar's experiences of the themes within the film - he was married to a transsexual (or a transvestite, i forget), he was very involved in the La Movida cultural scene of the late 70's early 80's, he himself is a homosexual (i believe) etc

Well, I'd say "Todo sobre mi madre" shows a side of Spanish culture that historically hasn't gotten a lot of media attention. Mainstream culture in Spain tends to be on the conservative side, and you see it in everything from relatively conservative dress (i.e. lots of dark colors and beige) to a general de-emphasis of things like homosexuality. Almodóvar brings into focus some of the more marginalized, or at least less mainstream, aspects of the culture - aspects which are definitely there, just not usually so much in the spotlight.

Hi freakysteph
First of all, I gotta tell you that I'm spanish, so I think that I will be able to give you some experienced views on the topic (also remember that I'm Spanish if you notice any mistake!).
I don't know what is believed of Almodóvar and Spain around the world, but Almodóvar is definitely not what you'd call a typical Spanish culture representation. I love his movies and the way he is (at least the way he shows himself), but the atmospheres he describes in his films are not very common ones. I don't criticise this at all, in fact I believe that expecting every filmmaker to reflect in his movies what you can see everyday when you open your front door is a nonsense, but if you intend to take Almodóvar's movies as an example of Spanish culture I'd recommend you to take a view on other directors, such as Miguel Albaladejo ("El cielo abierto"), Adolfo Aristarain ("Martin (Hache)", "Lugares comunes"; he's Argentinian but works in Spain. These two films are amazing), Inés París & Daniela Fejerman ("A mi madre le gustan las mujeres"), Imanol Uribe ("El viaje de Carol"), Benito Zambrano ("Solas", a masterpiece), Iciar Bollain ("Hola ¿estás sola?", "Te doy mis ojos"), Ramón Salazar ("Piedras"), Ricardo Franco ("La buena estrella"), Montxo Armendáriz ("Silencio Roto", "Secretos del corazón") or Fernando Trueba ("La niña de tus ojos"). I think that this way you could improve your project, although I don't know if you will be able to get these movies in your country.
Coming back to "Todo sobre mi madre" (by the way, it's one of my favourite movies), I think that the most typical Spanish feature you can find in it is the way people treat another people, the warmth, the interest in each other. I'm not telling you that every Spaniard is like that, but I consider that this kind of behaviour is quite common here in Spain.
In the same line, the tendence to talk is something really present among Spanish people. You may find yourself talking about your life with somebody you don't actually know, and there's a tradition of people talking and talking to each other, maybe not saying much, but talking, always talking (notice that in "Talk to her", which I'm sure you've seen, Benigno tells Marcos to talk to her girlfriend).
I expect to be useful to you, good luck with your project!