So today, I found a sign for a "Evangelical Methodist Church." In light of the recent split in the Methodist denomination, it has me wondering: are they using "Evangelical" here to say which side of the split they are choosing, or does it not really mean anything related to that? Or are all Methodists "Evangelical"?
No, not at all. Methodism, as with most Protestant denominations, went through a time of theological division in the 19th century as Liberal Christianity grew.
If you're not familiar, Liberal Christianity largely stems from challenges to the doctrine of sola scriptura in the post-enlightment period. There was and is a range of positions, but most Liberal Christians challenge the spiritual authority of the scriptures in some way: by ranking human reason above scripture, but challenging the traditional received authors of the Bible's texts, or by rejecting the infallibility/inerrancy of scripture. Liberal Christianity has also often rejected the traditional Protestant doctrines of original sin, penal substitutionary atonement, or the wrath of God and the propitiatory work of Christ.
The division between Liberal and Evangelical Protestantism has cut through most Protestant denominations, including the Methodist denominations. (Pentecostalism/Charismaticism is usually considered part of Evangelicalism, but could be argued to be a third major division when modern prophecy is allowed to supersede scripture's authority in the church.) In the USA Liberal Protestant denominations are often called Mainline Protestants; in other parts of the world they may be called Liberal or Progressive. Some denominations are essentially entirely Liberal, others may be mixed between Liberal and Evangelical.
Note that the presence of the word "Evangelical" in a denomination or church's name no more ensures that its theology is actually Evangelical in nature than a country's name containing "Democratic" ensures that it is actually a democracy. So the Evangelical Lutheran Church in America is considered a Mainline denomination with generally liberal/progressive theology. Similarly there is a denomination called the Evangelical Methodist Church which split in the 1940s from a different Methodist denomination, and so has nothing to do with the recent conflict in the UMC. It is generally on the side of evangelicalism, but we should expect pockets of more liberal churches within it as in all denominations. It's not clear from your question if the sign you saw referred to this denomination or to some other Methodist church which called itself Evangelical; either way the name is not guaranteed to reflect what the church teaches and if you want to know more you'll need to ask them yourself.
The Evangelical Methodist Church is not a newly formed group created in response to the controversy over same sex marriage and homosexual clergy being embraced in the UMC.
The Methodist churches that disagree with the UMC on these issues will become part of a new association called Traditional Methodist.
It is ironic that a group holding to the old traditional view of homosexuality will be called the “new” group of Methodist.
A read through the Wikipedia entry on UMC reveals that Evangelical Methodist has been a denomination under the World Council of Methodist for some time. Whether or not some or all Evangelical Methodist will attach with the “new”traditional Methodist group remains to be seen.