For the last 8-10 yrs I've been good about pruning my climbing rosebush and its has thrived. This year I didn't get to it in February, as I usually do, now it's April and not looking great. Will it harm the bush if I do my usual pruning in April?
Normal time for pruning roses is mid-February to early-March. It's a little late now so proceed with some caution. I don't know how you normally prune so can't recommend that you just go ahead.
Do you normally do a severe pruning or an overall thinning of the plant? Any type of severe pruning at this point has the potential to reduce flowering because you may prune out the flower buds. Severe pruning may reduce the overall size of the rose for the season as well. Just keep this in mind as you prune so that you don't end up without flowers later on.
If there are many dead canes that can be removed without damaging the foliage then go ahead-that will help increase air circulation within the plant and help reduce disease problems later in the season. You can also shape the plant-keeping in mind that you may be pruning out some flower buds.
I hope this helps and happy gardening!