If you grow plants they like instead then you don't have the commitment of the feeder. If none come, you haven't wasted your time since the plants still look nice whether the birds are there or not.

You can put a feeder ,but must change the solution and clean the container every week in cool weather and more often in summer time.It took me 2 seasons before they actually came to a feeder but they have never stopped coming since then.I don't live higher up, but they do fly high and may come.Don't get discouraged if you don't see any the 1st season they will come if you put it.Sometimes they will bring their babies to show them where to get some food when its raining or is cooler and no natural nectar is available.You can grow plants that attract them and also have a feeder for them.

I'm not in a highrise, but over the years I've noticed that my feeder has to be out as soon as they start coming in March, or they don't come to it. It appears that they set their territories early on. If I put out my feeder as soon as the salmonberries start blooming I get lots of hummers - Rufous and Anna's

They tend to disappear in July. BTW, they love delphiniums

It's been said Rufous has a habit of following the native floral parade up the mountainsides during the course of the growing season, with youngsters only sticking around later - lured into unnatural behavior by feeders and maybe summer blooming garden flowers. Anna's is here most of the time, having recently extended its range north from Oregon and California - presumably in response to feeders and non-native winter-flowering plants being present here. Here I've had the latter species coming all winter to a planting of Grevillea victoriae, which produces its tubular flowers late summer to late spring.

Here's an update:
I finally saw my first visitor the other day but it only stayed for a short while at the feeder.
The Salvia, bee balm, and fuchsia are still waiting to bloom.
And I just found out my neighbor on the same floor has had a feeder for a while but with red food color.