One could get some notion by looking at some of the depictions of 8472 encounters with individual Borg, given that they are comparable in strength (Data is stronger by a fair bit, as you can see from his arm wrestling Locutus in BOBY and the way he manhandles them in 'Descent', but not dominating, as can be seen in how they got the drop on him in 'First Contact'). It's been a while since I've seen the relevant Voyager episodes, but I do believe it was not pretty, though.
That said, Data's reaction time and reflexes even without invoking 'high speed' is still far above the Borg as ever depicted and above any organic being shown, so he may prove a match to a single 8472 alien, but I wouldn't call it a sure thing by any means, and I would have severe doubts of his ability to take on more than one...
Just my 2 cents.