Magsfhy, it's illegal in Spain as it is in the UK for a child of that age not to be in a restraint wherever the child is seated.
Answers to your question are covered in Car seats for very young babies See especially Bobaol's post in there 15 Apr 2008 10:34 PM.
I guess in a taxi, which obviously won't cater for young children, you do your utmost to restrain them. 
This shop in Torrevieja could help http://www.holitots.com/
I had to search all your posts to try to find if you'd mentioned your location & you had (Cabo Roig) Please will you mind going to your forum profile & filling in your location which will be such a help when anyone's wanting to help you. 
This message was last edited by morerosado on 5/18/2008.