If you come into L'Aldea High Street from Tortosa and take the right hand turn towards Amposta go under the bridge and on the right hand side is a small curtain shop not sure of the standard of workmanship and I suspect you will need a good standard of Spanish to get your requirements across. You could always type and google translate you requirements and take it with you.
We got our curtains from the website below they have sales if your early you may pick up a bargain and the good thing is you can send them back if you do not like them.We got a few sets made of a sail cloth type material. It's not worth spending a fortune as most pastel colours fade with the sun (and the rain !!!!) The white blinds we obtained from Poland via ebay. The website shown is the UK version but they have on-line store in Spain.(Change sites by clicking on the flag at the bottom of the page) Most goods are mirrored throughout the various European sites) Beware of the reinvented ex-pat who is a curtain/blind expert (Since their arrival) They will rob you blind  ;D ;D. (Ask for references of previous work carried out)  ;)  

http://www.laredoute.co.uk/homeware-curtains-voiles-blinds/cat-490.aspx

I have just added the Spanish site for you as you can see they have a sale 60% off. Good Luck  ;)

http://www.laredoute.es/textil-deco-cortinas-visillos-y-stores/cat-490.aspx

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