It depends on what chorizo you get as they can have pretty big differences in fat content.
This is the average from Syns Online. Per 100g:
Green 14.5 syns
Red/EE 9 syns
Choose one thats not too fatty and youll be OK.
You dont need very much if you slice it very thinly and its tastier that way. Once its shared between however many people its not too bad and its a tasty way to use your syns.
Yeah they're just like a very hard spicy sausage really but with a lot more fat and stuff in. Just let us know when you get it what the nutritional info is and we can tell you how many syns is in it. Enjoy! x