[SalesForce] Standard vs Standard Price Book

Pricebook visibility is controlled through the sharing model. Create each price book and then click the share button on it and select the appropriate groups who can use it.

One caveat for developers, SOQL queries for price books do NOT respect sharing rules as you'd expect and will always return all price books in the results.

Any special reason why you can't have a small trigger?

trigger oppWorkaround on Opportunity(before insert, before update){
    for(Opportunity o : trigger.new){
        if(o.Pricebook2Id == null){
            o.Pricebook2Id = 'hardcoded id here';
        }
    }
}

Put the id of your standard pricebook and you're done (except developer sandboxes). Bit better way would be to waste 1 query to SELECT Id FROM Pricebook2 LIMIT 1.

You will still need to specify PricebookEntries for products you want to be selectable (but since you mention standard prices I assume you're aware of that).