Pam and I shop at Mercadona, San Louis and generally we are very happy with the experience there. The shop is large enough to cover most of our needs but not so large that it takes an age to find the all items on Pam's list.
However, we do have one major gripe with the shop and that is with people at the checkouts.
You see, Pam is used to the kind of service that she got in British supermarkets. When she shopped at Sainsburys, they would summon someone to help pack for her and they would place the scanned items so that packing was easy.
The same applies in most other British supermarkets including Tesco, Marks & Spencer and Asda. In those that don't have personnel to help pack, the assistants will help bag the items making sure that similar things go together.
Apart from three of the people at Mercadona who do place the items in a way that makes packing easy, the rest simply scan the items and then almost throw them down piling items on top of each other.
Then when they have finished piling everything in a jumbled mess, the unhelpful attendants look at you as if to say "hurry up, we have customers waiting". There is even one man who will walk away from the till rather than try to help.
Apart from making it difficult to pack, heavy items end up on top of fragile ones. It doesn't take a lot of common sense to realise that putting a bag of potatoes on top of cakes is not a great idea.
The three exceptions are more than helpful. They carefully place the items that have been scanned in a logical way, they put the wine bottles in the special bag that we take with us and even bring heavy items like bottles of water around to the trolley. We can only surmise these three have been trained properly, just a pity they can't pass that training on to the rest.