"We are hopeful that he will play a part in our next two home games," Lalas said. "But I will tell you right now, if for one instant we feel that either physically or mentally he is not 100% ready to go, he will not play for us nor will he play for England."
Lalas also admitted that his side had yet to fully reap the benefits of the former England skipper's arrival, but insisted it was a steep learning curve for all involved.
"You can plan all you want for the arrival of someone like David Beckham, but when that hurricane blows in, it is unlike anything you have ever seen," Lalas said during the annual Honda Symposium in Los Angeles.
"We have used it to the best of our advantage off the field. But the on-the-field aspect of it has yet to come to fruition."
With Beckham around, media from all over the globe have put the spotlight on the Galaxy - and the club has not done as well as expected.
"Playing under immense pressure is something the Galaxy needs to get used to," Lalas said. "Our team has struggled this year. Our team has failed to live up to expectations but our team has also gone through an incredible transition.
"The pressure that exists now for our coaches, for our players, the atmosphere and circumstances that exist now on at the Galaxy are unlike anything the league has ever seen.
"It's not an excuse but it is a recognition that we are in a new world basically."