The summon monster spell can be very useful and powerful, but one of the limiting factors is the ability to give summons complex commands. What's the point of your celestial eagle if you can't tell it to use the smite evil ability? While there are some ways of getting around some language restrictions, other times they are always in your face. Normally I would assume that issuing a command to a summons must come directly from the caster, otherwise if anyone could control them then they are way too dangerous. I think there was an NCIS episode where the Russian trained dogs did this. Could you summon something with true speech and relay instructions from it to the rest of your summons?
How do others get around the language restrictions? I know tongues works for most cases, and speak with animals covers most of the others. True speech (which I don't believe there are spells for) is the only one which does cover everything to my knowledge, except maybe some forms of telepathy.
I had another question which was similar but this expands the problem a little bit as it does not deal solely with tongues.
Update: While I specifically call out summon monster with the question, I want this to apply to all the summoning spells such as natures ally and stuff.