Depending the venue and lay-out around the stadia, but if you just hang out between morning and evening sessions you can often bump into some significant athletes and coaches. At Gothenburg I bumped into the Jamaican women’s sprinters and they were really playful, cracking jokes on the walkby.
One other thing worth doing is to case the periphery of the stadium and find some little bar and restaurant slightly out of the way where you can chill between sessions if going back to your hotel for a rest is too inconvenient. Make friends with the people who work there, give them a souveneer from your country of whatever and they might be happy for you to use their toilet even when you’re not dining there. Finding a little place for respite can be valuable. You do need to eat something healthy occasionally if only to keep your strength up and you may find prices inside the “official area” somewhat rich.
Is there a full warm-up track there now? There used to be the grass fields up top behind the start area and some strips in the Marathon tunnel behind the start area.